publications of the 1NSTITUTE of MARINE SCIENCE Volume 8 / November, 1962 Published by the lnstitute of Marine Science The University of Texas Port Ar ansas, Texas In Memoriam SAM AND JoE GAMPERT October 1961, after Hurricane Carla. New Research Building and Boat Basin built w ith $439,000 from The University of Texas, National lnstitute of Health, and the National Science Foundation. publications of the 1NSTITUTE of MARINE SCIENCE Volume 8 I November, 1962 Published by the lnstitute of Marine Science The University of Texas Port Aransas, Texas PUBLICATIONS OF THE INSTITUYE OF MARINE SCIENCE Staff for Volume 8 Howard T. Odum, Editor John C. Briggs, Associate Editor William N. McFarland, Associate Editor Mrs. Anne Wilkey, Technical Editor The Publications o/ the lnstitute o/ Marine Science is printed annually by The University of Texas and includes papers of basic or regional importance by Gulf workers or on Gulf waters, in the fields of Bacteriology, Botany, Chemistry, Geology, Meteorology, Physics, Zoology, and other marine sciences. Papers are read by three referees; papers by the editors are processed by the Chairman of the Budget Council. Authors should submit manuscripts by Christmas for the annual volume the following June. In most respects the Style Manual for Biological !oumals of the American lnstitute of Biological Science is used (2000 P St., NW, Washington 6, D.C.). Bibliographic abbreviations follow World List of Scientific Periodicals. EDITORIAL ADVfSORY COMMITTEE OF THE PUBLICATIONS W. Frank Blair, Department of Zoology, The University of Texas, Austin, Texas. Harold C. Bold, Department of Botany, The University of Texas, Austin, Texas. Albert Collier, A. and M. College of Texas, College Station, Texas. R. L. Folk, Department of Biology, The University of Texas, Austin, Texas. Marcus A. Hanna, Gulf Oil Corporation, Houston, Texas. Willis G. Hewatt, Department of Biology and Geology, Texas Christian University, Fort Worth, Texas. Donald W. Hood, Department of Oceanography, A. and M. College of Texas, College Station, Texas. Sewell H. Hopkins, Department of Biology, A. and M. College oí Texas, College 'Station, Texas. Clark Hubbs, Department of Zoology, The University of Texas, Austin, Texas. Edward Jonas, Department of Geology, The University of Texas, Austin, Texas. R. J. LeBlanc, Shell Oil Company, 'Houston, Texas. Howard T. Lee, Texas Game and Fish Commission, Austin Texas. W. Armstrong Price, Wilson Building, Corpus Christi, Texas. Cecil Reíd, Sportsman CIU:b oí Texas, Austin, Texas. Robert O. Reid, Department of Oceanography, A. and M. College of Texas, College Station, Texas. AVAILABLE ISSUES Volume Number Year Pages tList Price I 1 1945 190 (out of print) I 2 1950 194 (out of print) 11 1 1951 212 $2.15 11 2 1952 215 $2.40 III 1 1953 224 $2.15 III 2 1954 131 (out of print) IV 1 1955 302 $2.65 IV 2 1957 341 $4.15 5 * 1058 492 $4.40. 6 * 1959 403 $4.15 7 * 1961 319 $4.15 8 * 1962 ( this volume) $4.15 *Standing orders for subscriptions may be placed at $4.15 per year. Please make check or purchase order payable to The University oí Texas. Since '1958 one volume has been printed per year (one issue). t Prices include postage. Please add 2% sales tax. INSTITUYE OF MARINE SCIENCE THE UNIVERSITY OF TEXAS PORT ARANSAS, TEXAS The lnstitute of Marine Science with laboratories at Port Aransas, Texas is a research division of The University of Texas related to the Departments of Microbiology, Botany, Chemistry, Geology, Physics, and Zoology and the Meteorology Division of the Department of Aerospace Engineering at the Main University at Austin. An integrated teaching program in graduate marine science is made up of the course offerings from the severa] departments and from the lnstitute. The permanent staff in residence at Port Aransas are primarily concerned with basic research with a general emphasis on functional processes in marine environments. During the summer, courses are given at the Institute for graduate students with serious interest in the sea. Staff and Students for 1960 INSTITUTE OF MARINE SCIENCE Howard T. Odum, Ph.D. (Yale), Director, Graduate Advisor, Lecturer (Zoology), Research Scien· tist V. Budget Council: W. F. Blair, Chairman; S. P. Ellison, Jr.; Harold Bold; H. T. Odum. ECOLOGY PROGRAM tRobert Beyers, A.B., National Science Foundation Fellow. tThomas R. Hellier, Jr., M.S., NSF Summer Fellow, TA in Zoology. t Ronald Wilson, M.A., Research 'Scientist 11. t Frank Little, M.S., Research 'Scientist l. Norman Vick, M.S., Technical Staff Assistant 111. Chester Runnels, M.S., Research Scientist l. John Meadows, Technical Staff Assistant 11. Richard B. Parker, A.M., Research Scientist 1 (Austin). Mrs. B. Beyers, Laboratory Research Assistant 11 (Austin). *Lamarr Trott, Research Scientist l. *F. 'Schlict, Tech. Staff. Assistant 11. *Maryanne Chilen, Laboratory Research Assistant l. *Richard Davis, Research Scientist l. *Niki Roberts, Laboratory Research Assistant l. • s. Bailey, Laboratory Research Assistant l. ·•1. Shanklin, Laboratory Research Assistant l. • 1. Messenger, Laboratory Research Assistant l. *Sister lean Francis Minner, A.B.,-'Student problem 380.l. MARINE MICROBIOLOGY PROGRAM Car! H. Oppenheimer, Ph.D. (UCLA & Scripps), Lecturer in Microbiology, Research Scientist V. •wmfried Gunkel, Ph.D., Consultant and Visiting Investigator, Helgoland, Germany. tW. G. Blanton, M.S., Research Scientist II. tMrs. M. Vanee Powell, M.S., Research Scientist I and TA in Microbiology. Reed Stevens, B.A., Technical Staff Assistant IV (in Antarctic). Floyd Clark, B.S., Technical Staff Assistant III. *Mrs. V. Wilson, Laboratory Research Assistant l. *Mrs. Patrick Parker, B.A., Laboratory Research Assistant II. *Mrs. Doris Blanton, Laboratory Research Assistant l. MARINE GEOLOGY PROGRAM Louis S. Kornicker, Ph.D. (Columbia), Lecturer in Geology, Research 'Scientist IV. Stuart Grossman, M.S., Research Scientist III. Charles D. Wise, M.S., Research Scientist II. tCharles M. Hoskin, M.A., Research Scientist II and NRC Fellow. tDarrel Jones, B.S. in Geology, Research Scientist I. *Glen Cosh, Laboratory Research Assistant II. • Edward Klovan, B.S., Volunteer assistant on Alacran (Columbia University). • Miles Hayes, M.S., student research problem 680.3 (Alacran reef). *Walter Pusey, B.A., student research problem '380.3 (Alacran reef). *Earl Behrens, M.S., student research problem 380.'3 (Alacran reef) . • Thomas Wright, Laboratory Research Assistant II. *Mrs. W. Rice, Curator of Mollusk collection. MARINE ICHTHYOLOGY AND PHYSIOLOGY PROGRAM William N. McFarland, Ph.D. (UCLA), Research Scientist IV, Lecturer in Zoology. Peter Pickens, Ph.D. (UCLA), Research Scientist III. tByung Lee, M.A., Research Scientist II. tCharles Powell, A.B., Research Scientist I and TA in Zoology. Emilio Guerra, Technical 'Staff Assistant l. *Charles B. Weil, Laboratory Research Assistant l. *]\frs. Edith Trott, B.A., Technical Staff Assistant II. *W. D. Anderson, Ph.D. (S.C.), Research Problem 380.5. MARINE CHEMISTRY PROGRAM Patrick L. Parker, Ph.D. (Arkansas), Research Scientist III, Lecturer in Chemistry. tHarry White, B.S., Research Scientist I. Robert Lawler, B.'S., Technical Staff Assistant II. *K. Robertson, B.S., Research Scientist l. •J. Pirson, Laboratory Research Assistant I. VISITING PROGRAMS ACTIVE IN 1960 *Robert Folk, Ph.D. (Penn.), Dept. of Geology, The University of Texas. •A. Cotera, M.A., Research Scientist l. *Emery L. Pierce, Ph.D. (Liverpool), Dept. of Biology, Univ. of Florida, Invertebrates. *Karen Hodges, Laboratory Research Assistant l. *L. V. Leboef, Student problem 480.1. *W. F. Wilson, Student problem 680.1. *Donald Boyd, Ph.D. (Colum'bia), Dept. of Geology, Univ. of Wyoming, Summer, Post-doctoral NSF Fellow. *James Larimer, Ph.D. (Duke), Dept. of Zoology, The University of Texas. *W. F. Blair, Ph.D. ('Mic'higan), Dept. of Zoology, The University of Texas. *J. T. Green, B.S., Research Scientist l. • W. A. Price, Ph.D. ( Hopkins), Corpus Christi. ADMINI'STRATIVE STAFF J ohn Thompson, B.B.A., Administrative Assistant. *Walter Garner, Administrative Assistant. *Roscoe Lamplugh, Technical Stafl Assistant III. Herman Moore, Motorboatman, (Ciencia). Joe Tracey, Plant Maintenance Mechanic (trainee). • Fred Breckwoldt, Maintenance Man ( summer). • Johnny M. Mathews, Maintenance Man (Small boats and motors). Mrs. Anne Wilkey, Technical Reports Editor. Mrs. Helen Brown, Senior Secretary. Mrs. Margaret Stewart, Secretary. • Mrs. Johnnie Morgan, Clerk Typist. • Mrs. R. Rogge, Secretary. • Mrs. B. Adams, Secretary. • sam Gampert, Building Attendant, (retired Aug. 31). Jesse Esparza, Maintenance Man. • Reece Brown, Laborer. • Mrs. V. Beyers, Food Service Supervisor II. NATIONAL SCIENCE FOUNDATION 'SUMMER STIPENDS FOR GRADUATE STUDY Walter Siler, W. D. Anderson, H. Ferguson, W. F. Wilson, M. Rayes, H. M. Bull, M. Kelley Staff and Students for 1961 Director and Graduate Advisor: Howard T. Odum Budget Council: W. F. Blair, Chairman; S. P. Ellison, Jr.; H. C. Bold; and H. T. Odum ECOLOGY PROGRAM Howard T. Odum, Ph.D., Research Scientist V. Lecturer in Zoology. tRobert Beyers, A.B., Research Scientist III. NSF Fellow. William Ogletree, B.S., Research Engineer II. tRonald Wilson, A.B., Research Scientist l. Rene P. Cuzon du Rest, M.A., Research Scientist l. Ronald Miller, B.S., Research Scientist Assistant l. Norman Vick, M.S., Technical Staff Assistant III. Miss Mary Ann Chilen, B.S., Technical Staff Assistant I. • James Markey, B.A., Technical Staff Assistant l. *Mrs. Barbara Beyers, Laboratory Research Assistant II. • Richard B. Parker, A.M., Research Scientist I. • John Ellison, Laboratory Research Assistant ( trainee). • John Shanklin, Laboratory Research Assistant ( trainee). *Steve Bailey, Labe>ratory Research Assistant ( trainee). *Re>bert Johnson, Labe>ratory Research Assistant ( trainee). • James Mohle, Laboratory Research Assistant ( trainee). • Richard Main, Laboratory Research Assistant (trainee). • Wayne F1enniken, Laboratory Research Assistant ( trainee). MARINE GEOLOGY PROGRAM Stuart Grossman, Ph.D., Research Scientist III. E. William Behrens, M.S., Research Scientist III. tWayne Horton, B.S., Research Scientist l. *Mrs. Winnie H. Rice, Curator of Mollusks. MARINE MICROBIOLOGY PROGRAM Car! H. Oppenheimer, Ph.D., Research Scientist V. Lecturer in Bacteriology. Chase Van Baalen, Ph.D., Research Scientist IV. Lecturer in Marine Microbiology. tGee>rge Blanton, M.S., Research Scientist II. tMrs. M. Vanee Pe>well, M.S., Teaching Assistant in Bacteriology. Reed Stevens, B.A., Technical Staff Assistant IV. F1oyd Clark, B.S., Technical Staff Assistant II. *Mrs. Lynn Parker, B.A., Laboratory Research Assistant II. MARINE CHEMISTRY PROGRAM Patrick L. Parker, Ph.D., Research Scientist III. Lecturer in Chemistry. *Harry White, B.S., Research Scientist I. Robert Lawler, B.S., Technical Staff Assistant II. *Loma McGough, B.S., Technical Staff Assistant II. • Ann Gibbs, Laboratory Research Assistant I. • Summer or intermittent. t Candidate for graduate degree, part time in residence. ICHTHYOLOGY-PHYSIOLOGY PROGRAM John C. Briggs, Ph.D., Research Scientist V. Lecturer in Zoology. William N. McFarland, Ph.D., Research Scientist IV. Lecturer in Zoology. Peter Pickens, Ph.D., Research Scientist III. tByung Lee, M.A., Research Scientist II. tCharles Powell, B.S., Research Scientist l. tFrank Little, M.A., Research Scientist l. tRobert Jones, B.S., Research Scientist l. Emilio Guerra, Technical Staff Assistant l. VISITING PROGRAM FOR 1961 J. Larimer, Ph.D., Dept. of Zoology, The University of Texas. tEhert Ashby, M.A., Research Scientist l. R. Folk, Ph.D., Dept. of Geology, The University of Texas. tMiles Hayes, M.A., Research Scientist l. tCharles Hoskin, M.A., Instructor in Geology, Naticmal Research Council Fellow. Reid Bryson, Ph.D., University of Wisconsin, Visiting Lecturer. Robert Ragotzkie, Ph.D., University of Wisconsin, Visiting Lecturer. E. J. F. Wood, Ph.D., Department of Oceanography, A and M College of Texas. *Chester Runnels, M.A., Research Scientist l. H. Hildebrand, Ph.D., Dept. of Biology, University of Corpus Christi. *G. Cosh, A.B., Research Scientist l. W. A. Price, Ph.D., Wilson Building, Corpus Christi, Texas. SUPPORTING STAFF John Thompson, B.B.A., Administrative Assistant. ÜFFICE ANO PUBLICAT!ONS Mrs. Anne Wilkey, Technical Reports Editor. Mrs. Helen Brown, Senior Secretary. Mrs. Margaret Stewart, Secretary. *Mrs. Harolene Hadden. Secretary. *Mrs. J. Morgan, Clerk Typist. BOATS Herman Moore, Motorboat Operator. Joe Tracy, Plant Maintenance Mechanic. *Otis Lewis, Laboratory Research Assistant (trainee) . *Johnie Mathews, Maintenance Man. PLANT ANO GROUNOS Jesse Esparza, Maintenance Man. Carroll Martin, Maintenance Man. Jesse Dickerson, Building Attendant. *Reece Brown, Lahorer. SUMMER KITCHEN Bob Burton, Food Service Supervisor. NATIONAL SCIENCE FOUNDATION SUMMER STIPENDS James W. Collinscm, Frederick K. Courville, Richard C. Fox, George H. Fraunfelter, Rohert S. Jones, Frank J. Little, Alline Marshall, Angel A. Maldonado, Verne R. Oberbeck, Ron Raschke, Alice E. Sharp, Frederick F. Wright. OTHER STUDENTS Ebert Ashhy, Mac V. Fraser, Wayne Horton, John Anderson Sherar, Ernest Tillman. t Candidate for graduate degree, part time in residence. * Summer or intermittent. Table of Contents lnstitute of Marine Science, Staff and Students for 1960, 1961 --------------------------------iii Fish Production and Biomass Studies in Relation to Photosynthesis in the Laguna Madre of Texas. Tlwmas R. Hellier, fr. ---------------------------------------------------1 Further Studies on Reaeration and Metabolism of Texas Bays, 1958-1960. Howard T. Odum and Ronald F. Wilson ---------------------------------------------------------------23 Sorne Bacteria! Populations in Turbid and Clear Sea Water Near Port Aransas, Texas. Carl H. Oppenheimer and Holger W. f annasch ----------------------------56 Algal Mat Communities of Lyngbya con/ervoides (C. Agardh) Gomont. Lazern O. Sorensen and fohn T. Conover ------------------------------------------------------------------61 Zinc in a Texas Bay. Patrick L. Parker ------------------------------------------------------------------------75 The Microbial Decomposition of Organic Carbon in Surface Sediments af Marine Bays of the Central Texas Gulf Coast. Carol M. Volkmann and Carl H. Oppenheimer ------------------------------------------------------80 Sorne Aspects of Osmotic and lonic Regulations in the Blue Crab, Callinectes sapidus, and the Ghost Crab, Ocypode albicans. Charles A. Gifjord --------------------97 Osmotic and lonic Concentrations in the Mantis Shrimp, Squilla empusa Say. Byung Don Lee and William N. McFarland -----------------------~-----------------------------------126 Phosphorus Content of Sorne Fishes and Shrimp in the Gulf Coast of Mexico. Kenneth T. Marvin and Larence M. Lansford ---------------------------------------------------------143 Chaetognatha from the Texas Coast. E. Lowe Pierce -------------------------------------------------147 An Ecological Survey of the Lower Laguna Madre ofTexas, 1953-1959. fose ph P. Breuer ------------------------------------------------------------------------------------------------__ __ _ 153 A Study of Redfish, Sciaenops ocellata Linnaeus and Black Drum, Pogonias cromis Linnaeus. Ernest G. Simmons and foseph P. Breuer ___________________ 184 Effect of Hydraulic Dredging on Sedimentation. Thomas R. Helüer, fr. and Louis S. Kornicker ___ ----------------------------------------------------212 Shrimp Landings and Production of the State of Texas for the Period 1956-1959, with a Comparison with Other Gulf States. Gordon Gunter -----------------------------------216 Marine Algae from the Gulf Coast of Texas and Mexico. H. f. Humm and H. H. Hildebrand ------------------------------------------------------------------------227 Phytoplankton of the Eastern Mississippi Delta. Ernest G. Simmons and Wüliam H. Thomas ----------------------------------------------------------269 Fishes of Rio Tamesí and Related Coastal Lagoons in East Central Mexico, with Notes on their Distribution, Ecology, and Zoogeographic Relations. Rezneat M. Darnell -----------------------------------------------------------------------------------------------299 Mollusks of Alacran Reef, Campeche Bank, Mexico. Winnie H. Rice and Louis S. Kornicker ------------------------------------------------------------------366 Chronological Record of Contributions from the Institute of Marine Science 1945-1960 -----------------------------------------------------------------------------------------------------------------394 Fish Production and Biomass Studies in Relation to Photosynthesis in the Laguna Madre of Texas1 2 • THOMAS R. HELLIER, JR.3 lnstitute o/ Marine Science and Department o/ Zoology The University o/ Texas Abstract The rate of growth of populations of animal consumers depends to a considerable extent on the rate of food supply derived from photosynthetic production of plant material either within the com­ munity or that imported into the community. Yet few studies directly relate fish production to plant production. In the present study, an effort has been made to relate fish production to gross plant production in a shallow, frequently hypersaline coastal bay, the Upper Laguna Madre of Texas. The Upper Laguna Madre is located on the Texas Gulf Coast immediately south of Corpus Christi Bay, and is separated from the Gulf of Mexico by a narrow barrier island, Padre Island. Biomass estimates of the animal species present were determined with a new population sampling device, the drop-net quadrat. The principie of this method is to instantaneously isolate a segment of the study area with its natural fish population, and by extrapolation determine the approximate density of the fish population of the area. Twenty-nine samples were taken overa 17 month period from March, 1958, to August, 1959. Age and growth estimates of the dominant fish species were determined by scale analysis, and by reference to length frequency histograms. A total of 31 species were taken during the study, five of which constituted approximately 70 percent of the biomass. These five species were: Mugil cephalus, Lagodon rhomboides, Leiostomus xanthurus, Anchoa mitchilli, and Menidia beryllina. Fish production as used in this paper was defined as the weight increase of the fish per unit time while the fish were in the study area. The monthly weight increases for ali of the individuals collected during each month we-e totaled and placed on a per acre basis. Primary gross plant production was measured by the diurna! oxygen method with oxygen samples taken every three hours over a 24 hour period. Biomass estimates of fish and larger invertebrates ranged from a summer maximum of 337 pounds per acre (37.8 g/m2) to a winter minimum of 18 pounds per acre ('2.0 g/m2). The annual fish produc­tion estimate was 137 pounds per acre ('15.4 g/m2 dry weight) as compared with an annual gross primary plant production estimate of 4177 g/m2/yr expressed as oxygen. The seasonal migration and growth of fish stocks are in phase with the primary production of food. lntroduction The rate of growth of populations of animal consumers depends to a considerable extent on the rate of food supply either derived from photosynthetic production of plant material within the community or imported into the community. Yet few studies directly relate fish production to plant production. 1 From a dissertation presented to the faculty of the Graduate Sch0<>l of The University of Texas in partial fulfillment of the requirements for the degree of Doctor of Philosophy. This study was supported by the Marine Division, Texas Game and Fish Commission through an interagency contract, Dr. H. T. Odum, Principal Investigator. 2 Contribution No. 55 from the Marine Laboratory, Texas Carne and Fish Commission, Rockport, Texas. 3 Present address: Department of Biology, Arlington State College, Arlington, Texas. Fish Production and Biomass Studies Harvey ( 1950) in a study of the English Channel and Riley ( 1955) in Block Island Sound estimated that in terms of carbon content fish use 0.52 to 0.65 per cent and 0.4 to 0.8 per cent of the net phytoplankton production respectively. Harvey's estimates from the English Channel agree well with those given by Riley for Block lsland Sound, showing a possible direct relationship between photosynthesis and fish production. A close relation between photosynthesis and growth of juvenile salmon was indicated by Nelson (1958) for a fertilized Alaskan lake. This relationship was evident even though the fish involved was a secondary and tertiary consumer. However, Riley (1955) sug­gests that the efficiency of conversion of plant material to animal production may vary from one type of habitat to another. For example, brackish coastal waters constitute an environment which favors the dominance of nanoplankton (Ryther, 1954). Riley ( 1955) suggests that nanoplankton are less efficiently used by large zooplankton and therefore result in a dissipation of available energy by bacteria and microzooplankton. In general, the shorter the food chain involved, the more efficient is the transfer of photosynthetic products to the higher trophic levels in the community. In a study of fish production on a Bermuda coral reef, Bardach (1959) found a high rate of efficiency of conversion of total solar energy to fish (0.0014% ) as compared to that (0.00025%) reported by Clark (1946) for the commercial landings of fishes on George's Bank. The total fish production is probably much greater than the commercial landing. However, even by doubling Clark's efficiency estímate, it is just overa third of Bardach's. Odum and Odum (1955) and Odum, Burkholder and Rivero (1959) showed that utilization of solar energy by reef plants is higher than in many other communities. This high plant efficiency of coral reefs may account, at least in part, for the more efficient conversion of solar energy to fish production in that habitat. Total solar radiation was compared with fish production by Hayne and Ball (1956) in a shallow Michigan pond and the same efficiency value was found (0.0014%) as Bardach presented for a coral reef. Per­haps higher fish production per calorie of solar radiation could be explained by better transmission of light, a higher plant efficiency in very shallow waters, a shorter food chain, or a channeling of solar energy into plant material that is more available to consumers. Quantitative studies of fish stocks and fish production have not been conducted in bays heretofore because methods were not available. Reliable methods have not been available for measuring the biomass of fishes per area. Most sampling methods are also selective in so far as size of fish is concerned ( Carlander, 1956). lt usually is most difficult to collect a representative sample of an entire fish population, since different age groups of a species and different species often have different ecological requirements and are not uniformly distributed. Quite often population and production studies in marine fisheries work are geared to consider only the economically important or easily sampled size ranges of a single species. Sorne notable exceptions are works by Merriman and Warfel, 1948; Harvey, 1950; and Bardach, 1959. Production studies on marine fishes have been conducted primarily on commercially exploited populations such as the North Sea Haddock, Gadus aeglefinus, (Margetts and Holt, 1948). Although this type of study may have considerable value in establishing management policies for a particular fishery, it is difficult to evaluate the ecological economy· of the individual species unless its role is known in the overall production of the community. In the present study an effort has been made to relate fish production to gross plant production in a shallow coastal hay, the Upper Laguna Madre of Texas. The Laguna Madre receives little river water, or water from the open sea, and thus its fish popula­tions are dependent directly or indirectly on plant food produced in the hay. In this study an effort is made to include all of the larger species of consumers. Fortunately, segregation of fishes by size and species in the Upper Laguna Madre is minimized due to the relative homogeneity of the available habitat in the hay. Description of the Upper Laguna Madre The Upper Laguna Madre is one of a series of shallow coastal bays located on the Texas Gulf Coast (Fig. 1) immediately south of Corpus Christi Bay. The Padre Island Causeway (a landfill) delimits the northern boundary of the area under study. The Upper Laguna Madre is separated from the Gulf of Mexico by Padre Island, a narrow barrier island, and the southern boundary of the hay is delimited by a semi-dry bar extending from Padre Island to the mainland. This bar is 35 miles south of the Padre Island Causeway. The Upper Laguna Madre is three to five miles wide at mean low tide. A canal, the lntracoastal W aterway, 125 feet wide and 12 feet deep runs north­south bisecting the hay. Spoil banks from this waterway form a nearly continuous island paralleling the canal for 13 miles south of the northem boundary of the hay. From this point south the intracoastal spoil banks are staggered. Water circulation between the Upper Laguna Madre and adjoining bays is limited by the causeway at the northern end which has three openings totaling less than 1,500 feet at normal tide levels, and by the bar at the southern end which has only one opening slightly wider than the lntracoastal Waterway. These constrictions of the hay restrict circulation. In times of low precipitation, a hypersaline condition develops. Fish Production and Biomass Studies A considerable volume of research has been accomplished in the Upper Laguna Madre. The most recent are measurements of community metabolism and chlorophyll by Odum and Hoskin (1958), and Odum, McConnell and Abbott (1958), andan ecological survey by Simmons ( 1957). Simmons' survey contains a physical and biological descrip­tion of the area. Hedgpeth ( 1947) discussed salinities, fish yield, tidal exchange, and pass cutting prior to the dredging of the lntracoastal Waterway in 1948 and construc­tion of the Padre Island Causeway in 1950. He also has listed severa! organisms from the hay (Hedgpeth, 1953). Gunter (1945a) reviewed attempts to dredge a pass to the Gulf through Padre Island. Salinities over a period of years have been reported by Burr (1930), Baker ( 1949) and Collier and Hedgpeth (1950). Pearson (1929) worked on the life histories of sciaenid fishes in the area. A general ecological study on Baffin Bay, a tertiary hay opening into the Upper Laguna Madre, 21 miles south of Padre Island Causeway (Fig. 1) was conducted by Breuer ( 1957). The northern portion of the hay is very shallow, ranging from one to three feet deep in the zone extending for 13 miles south of the causeway, where there is a natural basin approximately five feet deep. This basin delimits the southern boundary of the present study area (Fig. 1). The shallow portion of the Upper Laguna Madre was covered with a dense growth of shoalgras.s (Diplanthera wrightii) and widgeongrass (Ruppia mari­tima). Acetabularia crenulata was frequently encountered in the area though never abundant. Due to the extreme restriction of water exchange between the Upper Laguna Madre and its neighboring bays no daily lunar tides were perceptible. However, the hay was affected by wind tides and prolonged raising or lowering of the general Gulf tidal level. This long period tidal effect is illustrated by Table l. This entire northern portion of the hay was extremely homogeneous ecologically, and comprised approxi­mately 27,000 acres. Five general sampling areas were established in the study area (Fig. 1). Average monthly depths are presented in Table 1, and average monthly salinities and tempera­tures in Fig. 2. TABLE 1 Average monthly water depth in meters at station 2 March, 1958 April May June July August September October Novem'ber December January, 1959 February March April May June July 0.33 0.41 0.91 0.76 0.66 0.63 0.81 1.23 LOO 0.66 0.50 0.41 0.59 0.89 1.00 0.69 Material and Methods Active field work was conducted from March, 1958, through August, 1959. Simul­taneous measurements were made of gross photosynthesis, biomass of fishes, and sorne dominant invertebrates every month. ROPES HOLDING PART OF N[T IM [LEVATED POSITIOH ~--"""\ ~ F1c. 3. Drop-Net Quadrat. Biomass estimates were determined with the drop-net quadrat described by Hellier ( 1959) Fig. 3. The principie of this method is to instantaneously isolate a segment of the study area with its natural fish population and by extrapolation determine the approximate density of the fish population of the area. A description of the drop-net quadrat method of population sampling follows. A quadrat is surrounded with a small mesh net This net is supported by a steel cable suspended approximately three feet above the surface of the water from eight pilings. A heavy chain (one pound per foot) is used for a lead line on the net. A line is secured to the chain at each piling. These lines are passed through pulleys located on crossarms at the top of the piling, and the net is hoisted clear of the water. After the lines are secured to a trigger mechanism the net is ready to drop. In the study, quadrats of two sizes were used, one 50 feet square (1/16 acre, 252.9m2 ) and the other 100 feet square (% acre, 1011.7m2). The same netting was used on all quadrats. This netting was made of nylon material of number nine thread with % inch square mesh on an eight foot drop from top to bottom. Care was taken to maintain the netting in perfect repair to assure the retention of all fish. Between six and ten hours were allowed to elapse between the setting and the triggering of the drop-net quadrat. Triggering of the net was always done at night to reduce effects of shadows from the overhanging net. F-ish Productwn and Biomass Studi-es Fish were removed from the drop-net quadrat by two methods. The larger fish in the quadrat were captured by seining with a 11/2 inch square mesh trammel net 300 feet long, and the smaller fish were taken with a 120 foot hag seine of % inch square mesh with a 12 foot bag in the center. Seining was continued in the enclosed quadrat until no more fishes were caught. The numher of hauls required to remove the fishes from the quadrat varied from a mínimum of five in periods of low population density to 14 in a period of greater density. However, most of the fishes were removed in the first two seine hauls. Table 2 lists the biomass taken per sample. TABLE 2 Biomass estimates from the drop·net quadrat per sample, compared with sorne environmental conditions, from March, 1958, to August, 1959 Bioman, pounds per acre Dale Trap oo. M.,Pl cephal"' Other fi sh .. In verle· brales Temp. ºC Sal. %o E1timated wind velocity, mph March 7, 1958 2 31.5 0.3 18.0 '22.5 calm March 14, 1958 2 4.8 0.6 '12.0 1'2.0 20NW March 20, 1958 '2 7.7 6.5 18.0 19.0 SENE March 28, 1958 2 8.2 9.8 16.5 23.0 lOSE April 16, 1958 2 28.0 65.8 79.4 21.0 20.5 lOSE May 22, 1958 2 57.6 100.8 99.6 26.0 23.5 SNW June20, 1958 '2 292.0 '323.9 '12.3 30.0 37.5 20SE July9, 1958 4 4'1.5 4'2.2 31.6 30.0 43.0 lOE rain July 17, 1958 2 86.4 '109.3 8.5 30.0 50.0 SSE August 10, 1958 3 71.4 110.7 2.6 29.0 56.0 SSE August 19, 1958 4 44.2 153.8 5.1 31.0 57.0 15'SE September16, '1958 4 86.1 148.6 27.6 28.0 24.5 25ESE September'29, 1958 3 17.4 54.9 9.6 26.0 35.0 calm October 9, 1958 4 46.1 104.9 36.2 28.0 42.0 20ESE October 24, 1958 3 o 26.3 0.3 25.5 32.0 calm November 12, 1958 4 7.0 24.2 4.8 '23.8 31.0 lONE November 20, 1958 3 6.7 25.1 3.7 '21.0 30.0 December 5, 1958 4 o 18.5 l'l.8 16.'2 30.0 SSE Decemher 10, 1958 3 3.5 19.2 17.5 13.5 25.0 '25NE January 23, 1959 3 o 3.'8 2.0 9.2 24.0 5NE January 29, 1959 5 7.5 13.6 16.5 15.0 25.0 calm February 4, 1959 4 '18.5 23.6 0.3 10.0 24.0 SSE Fehruary 24, 1959 5 18.3 88.9 0.5 14.5 '25.0 lONE March 10, 1959 3 8.0 56.1 5.9 16.9 27.0 15 E March 24, 1959 5 7.6 42.0 6.4 '19.1 '27.5 10 ESE April 22, 1959 5 101.7 '120.8 8.'3 19.l 28.0 SSE May 25, 1959 4 24.0 41.9 8.'l 27.0 29.0 20SE June 19, 1959 4 29.0 57.4 17.2 27.0 24.0 IOESE July 17, 1959 5 67.8 81.8 4.1 '28.0 30.0 15SE The reliability of this method is thought to be good in the shallow study area. Samples taken at different stations during periods of stable environmental conditions show a close correspondence as illustrated by the July 7-August 10, 1958 samples and the November samples. The principal sources of variation were sudden environmental changes, which tended to cause the fish to move from the shallow vegetated study area into deeper water, and the intrinsic migrations of the fishes, such as the spawning migrations. The effect of sudden changes in the environment is evident in the July 9, 1958 sample taken during a period of rainy weather, the September 29, 1958 sample following the first sudden temperature drop of the year, and the January 23, 1959 sample made during a period of extreme cold weather. The absence of the breeding population of the striped mullet is reflected in the late fall, winter, and early spring samples. Migrations of the individual species are discussed under the species headings. Ali specimens were preserved in the field in ten per cent formalin. Measurements, weights, and scale samples were taken in the laboratory, and a representative sample of each species was preserved in 40 per cent isopropyl alcohol. Standard lengths and total lengths were measured to the nearest millimeter, and wet weights were taken on a triple beam balance to the nearest tenth of a gram. Ali length measurements are given here as standard length. Temperatures were taken to the nearest tenth of a degree centigrade. Depth at the station was estimated to the closest centimeter, and salinity was analyzed to the nearest half of a part per thousand by either a calibrated hydrometer or torsion balance salinom­eter. Supplementary collections of fishes were made with the bag seine and with a 16 foot otter trawl having one inch square cod end mesh. Age and growth of the mullet Mugil cephalus were determined by scale analysis. Scales were placed between glass slides, projected in a 2 X 2 inch slide projector, and examined on a screen at a magnification of 18x. Conversion of scale measurements to fish lengths was accomplished with a nomograph similar to that described by Hile (1948). Estimates of primary production were procured by use of the diurnal oxygen calcu­lation method described by Odum ( 1956), and Odum and Hoskin ( 1958). Odum and Hoskin discuss the reliability of this method for the Upper Laguna Madre. Oxygen samples were taken every three hours over a 24 hour period at station two, and analyzed by the Winkler method. A four year record of production in the area is given by Odum and Wilson ( 1962) in this volume. Standing Crop and Production of Fish Populations A total of 31 species of fish was taken in the drop-net quadrat. Five of these species constituted 70 per cent of the fish biomass, and of the remaining 26 species six were not considered resident members of the fish population in the Upper Laguna Madre. Each species is considered separately in order of decreasing abundance. Mugil cephalus LINNAEUS-STRIPED MULLET Mugil cephalus is one of the most abundant fish in shallow Gulf waters. Gunter (1941) listed it as one of the four most abundant fishes of the Northern Gulf Coast, and Joseph and Yerger ( 1956) list the mullet as first in terms of species mass for Alligator Harbor, Florida. Thus it was not surprising that the striped mullet maintained the highest bio­mass of any fish species in the study area. This species is apparently well adapted for the broad salinity changes in ,the Upper Laguna Madre. It has been reported from chlorinities of less than ten ppm (Hellier, 1957) and from salinities in excess of 75%0 (Simmons, 1957). Mullet of zero year class entered the Upper Laguna Madre in January at about 25 mm but at no time during their first year were fish of this group taken in large numbers. lt is probable that very small mullet in Texas waters have habitat requirements similar to Cyprinodon variegatus, and move into open hay waters only after attaining greater Fish Productwn and Biomass Studi.es size. Kilby (1949) describes this type of behavior for small mullet in Florida. Young mullet first entered the drop-net quadrat catch during January at approximately the end of their first year. The mean size of this group was 116 mm. Subsequent age and growth of striped mullet were determined by scale analysis. The validity of this method for Mugü cephalus has been shown by Broadhead (1958) in Florida, and by Thompson (1951) in Australia. The mean size at annulus formation for Texas mullet is compared with the data of other authors in Table 3. TABLE 3 Mean standard length of Texas mullet from scale analysis compared with data of other authors Age in years Area Texas (present study) --------------------· 116 Texas (Gunter, '1945b) * _ -----·--------·· 81-117 Pensacola, Florida (Broadhead, 1958) t _ 122 Homosassa, Florida (Broadhead, '1958) L 153 Georgia (Anderson, '1958) 160 Australia (Thompson, 1954) t ___ 121 181 230 '1:77 324 178 226 231 '1:74 314 ···-­203 2'82 342 398 430 474 * Converted to standard length using 0.79 limes total length. t Converted lo slandard length using 0.86 times fork length. Production estimates for this species in the Upper Laguna Madre (Fig. 4) are based on the average monthly growth of the individual fish taken in the drop-net quadrat. Striped mullet in the Upper Laguna Madre show a mean weight increase of 31 gm for the first year, 84 gm for the second, 116 gm for the third, and 167 gm for the fourth. No estimate of mortality, emigration, or immigration was made. However, the effects of these phenomena in the production estimates are minimized by the use of monthly rather than annual production computations. Lengths may be converted to weight by the following length weight equation. Log W = -4.54 + 2.92 Log L Where W = weight in grams L = standard length in mm Thompson ( 1954) summarized a number of food studies on Mugü cephalus. These studies indicate that striped mullet are primarily herbivores. A recent study by Darnell (1959) in Lake Ponchartrain shows the striped mullet to be iliophagous. Lagodon rhombowes (LINNAEUS )-PINFISH Biomass estimates indicate that pinfish were the second most abundant fish in the Upper Laguna Madre. Lagodon rhomboides is one of the most ubiquitous fish in shallow marine water and has been taken abundantly in salinities as low as l.05%o (McLane, 1955) and as high as 75%0 (Simmons, 1957). Gunter (1945b) gave a temperature range for Texas pinfish from 9.1 ° to 34.9ºC. During the present study this species was found to be quite active in the Laguna Madre ata temperature of 7.6ºC. Young pinfish appeared in the shallow waters of the Upper Laguna Madre during March or April at a mean length of 25 mm (Fig. 5). The nurnbers of young pinfish continued to increase in the sample area through June, and then began to decline (Fig. 6). Assuming that sampling was random, this decline indicates emigration and Fish Productwn and Biomass Studies s rANOARO LENGrH IN MILL/MErERS lu -..J ¡¡_ ~ '<:( Vi l.._ C) ..... ~ lu \.) Cl:: lu ¡¡_ ~ ~ \.) ~ lu :::i C) lu Cl:: l.._ Frc. 5. Length frequency of Lagodon rhom­boides from the drop-net quadrat in the Laguna Madre, March; 1958--July, 1959. JO --Nur.iber/acre 28 -Pounds/acre Biom 26 26 -----Pounds/acre Production 24 24 / 1 o o 22 22 M 1 1 20 20 1 1 18 ." 18 1 1 o. 16 16 1 1 ~ 14 1 1 14 ·~ 1 1 ." o 12 12 1 \ 10 10 ~ ) ¡\ \ / \ \\ : \ :~ \1'1 ; \ ! ' '~ /\ 1 .. '' I>'\.._ ,,,v. ' / \f \'i':...... ~ i \,/ \ V \,. ....-r~- Frc. 6. Biomass, production, and number of Lagodon rhomboides from drop-net quadrat in Laguna Madre, March, '1958-July, 1959. Yearly production may be determined by t<>taling the production shown for each month. mortality for the population of the area. lt is interesting to note that only 4.8 per cent of the June population were found in the area in February. If a similar number of fish were removed from the population in April and in May as in June, no more than two per cent survived until February. Very few pinfish in the second year class were found in the shallow vegetated sample areas, but supplementary trawl hauls in the channels and boat basins of the Upper La­ Fish Production and Biomass Studies guna Madre yielded moderate numbers of larger fish throughout the year. Caldwell (1957) states that Lagodon evidently spawns in the open ocean, and Hildebrand and Cable ( 1938) suggest that this species matures in its second year. lt is possible that a majority of the second year fish leave the study area and move toward the Gulf, or into deeper hay waters. Length frequency data from the drop-net quadrat indicate a growth rate for pinfish slightly greater than that given by Caldwell (1957) for Florida, but very similar to rates found by Gunter (1945h) for Texas, and Hildehrand and Cable (1938) for North Carolina. Lagodon rhomboides in the Upper Laguna Madre increases from an average of 25 mm in March to an average of 99 mm in Fehruary. This involves a weight in­crease of approximately 27 g per fish or 2.25 g per fish per month. Production estimates were calculated by' multiplying the numher of fish taken per month (Fig. 6) times the monthly growth rate as takert from the length frequency histogram. Lengths may he converted to weight by using the length weight equation given by Caldwell (1957). Log W = -4.3í34 + 2.9136 log L Where W = weight in grams L = standard length in mm Monthly hiomass and production estimates are presented in Fig. 6. The pinfish evidently occupies more than one trophic level. Literature records as sum­marized by Caldwell (1957) show the pinfish as apparently completely indiscriminate in food habits, although more animal than plant material was reported, particularly in the smaller fish. A recent food study by Darnell (1959) tends to support the above statement. Leiostomus xanthurus LACEPEDE-SPOT The spot was the third most abundant fish taken in terms of biomass during the pres­ ent study. Ecologically it is well adapted for the Laguna Madre. Reid (1957) observed a marked gradient distribution of young individuals in East Bay, Texas, with the largest concentrations in lower salinity. However, Kilby (1955) 'and Simmons (1957) indicate that habitat may have a greater influence on young spot than salinity. Dawson (1958) described the spot as extremely euryhaline, and Simmons (1957) reported itas common in the Laguna Madre in salinities up to 60 %o· Length frequency curves indicate that young spot enter the catch in the Upper Laguna Madre during March or April at a mean size of 20 mm (Fig. 7). These fish apparently remain on the nursery grounds in the Laguna until their second year. Large spot in the second and third year classes leave the bays in late fall and winter, and move into the Gulf to spawn. A majority of these fish in Texas waters do not survive to re-enter the bays ( Pearson, 1929; Gunter, l 945b) . Growth rates for the spot were determined from length frequencies. Growth rates are very similar to those presented by Townsend (1956) and Dawson (1958). Young spot enter the Upper Laguna Madre in March at a mean length of 20 mm. These fish reach a length of approximately 125 mm by the following February and according to Town­ send (1956) 150 to 185 mm at the end of the second year. This involves an overall weight gain per fish of 50 to 55 g for the first year in the Laguna or 4.2 g per month, and an average gain for the second year of 85 g or seven grams per month. Production estimates were calculated by multiplying the number of fish taken per month (Table 4) Fish Productwn and Biomass Studies srANOARO LéNGrH IN MILLllllETéRS 17 \\ '-. 16 lS 14 l) 12 . ll . ~ 10 .. " i.8 R. PIAJllJJASONDJPPIAP!JJ FrG. 8. Biomass and production of Leiostomus xanthurus from the drop-net quadrat in the Upper FIG. 7. Length frequency of Leiostomus xan­Laguna Madre, March, 1958-July, 1959. Yearly thurus from the drop-net quadrat in the Laguna . production may be determined by totaling pro· Madre, March, 1958-July, 1959. duction shown for each month. TABLE 4 Number of Leiostomus xanthurus per acre from the Laguna Madre March, 1958-May, 1959 N umber per acre Month Year class O Year class l March 1;192 o April 1,856 o May o o June 32 o July 132 o August 264 34 September 24 34 October 68 8 November 40 o December 72 o January 16 4 February 148 116 March 4 36 April 4 4 May 44 o times the monthly growth rate as taken from the length frequency histogram. Lengths may be converted to weight by' using the length weight equation given by Dawson (1958). Log W = 4.54396 +2.95831 Log L Where W = weight in grams L =standard length in mm Monthly biomass and production estimates for L. xanthurus in the study area are shown in Fig. 8. Food studies by many authors as summarized by Dawson (1958) place the spot in a tertiary trophic level feeding on the lower trophic levels such as annelids, ostracods, and copepods. Anchoa mitchilli diaphana HILDEBRAND-BAY ANCHOVY Numerically the hay anchovy was the most abundant species found in the study area, but in biomass it was fourth. Gunter (1945b) suggests that this species may· be more abundant at low salinities al­though it is euryhaline and very abundant over a wide salinity range. Simmons (1957) encountered A. mitchilli at salinities as high as 80%0 in the Upper Laguna Madre. Very few specimens of this species were taken in the drop-net quadrat during late spring and early summer. The length frequency data obtained from the drop-net quadrat does not allow determination of the spawning season, because the mesh size of the netting retained 25 mm and larger individuals only. However, Gunter (1945b) indicates a prolonged season from spring through fa!!. Reid ( 1956) suggests that at least two age groups are present in East Bay, Texas during June, one group with a mode near 30 mm and another with a mode at 40 mm. lt is not possible to separate these age groups during most months from the length fre­quency data obtained in the present study (Fig. 9). However, a group with a mode at 25 mm entered the catch in March, 1958. This group may represent a late summer or early fall spawning. They reached a length of 32 mm in August and 35 mm in Sep­tember, which in all probability terminates the first year's growth for the group. This same group reaches 45 mm by the following March and then can be traced no further. These larger A. mitchilli left the study area during the summer months either as a result of high spawning mortality or emigration. The September group averages 0.407 g per individual which represents 0.034 g per month weight increase while the 45 mm group from March averages 1.03 g or a gain of 0.104 g per month. Production estimates for A. mitchilli are based on these growth statistics even though growth was probably slightly slower in the winter months and faster during the remainder of the year. Only those specimens large enough to be taken in the drop-net quadrat were considered; consequently, a large part of the first year's growth was not included in the production estimates. Biomass and production estimates for the hay anchovy are given in Fig. 10. Reíd (1955) states that this species feeds on the lower trophic levels. Darnell (1959) lists zooplankton as the primary food source of this species. Menidia beryllina península.e (GooDE AND BEAN)-GULF SILVERSIDE The silverside is one of the most frequently encountered fish in Texas tidal waters (Gunter, 1945b). However, it was not found to be as abundant in the Upper Laguna Madre during the present study as the larger species, Lagodon rhomboides or Anchoa mitchilli. Not ali of this species were caught in the sampling gear used. Menidia below Fish Production and Biomass Studies STANOARO LENGTH IN MILL/METERS mitchüli from the drop-net quadrat in the Upper FIG. 9. Length frequency of Anchoa mitchilli Laguna Madre, March, 1958-July, 1959. Yearly from the drop-net quadrat in the Laguna Madre, production may be determined by totaling pro­March, 1958-July, 1959. duction shown for each month. 30 mm were able to pass through the netting of the drop-net quadrat at will and fish from 30 to 35 mm were commonl y found stuck in the meshes. The largest biomass of silversides was found during the winter months although this again may have been an artifact of sampling, as the summer and fall populations are composed largely of fish too small to be held by the drop-net quadrat. The silverside is a fish with a very short life cycle. Bayliff (1950) suggests for Menidia menidia that the average life span is only one year. Gunter (1945b) indicates that Menidia beryllina does not survive past spawning which takes place at the end of the first year, while Bigelow and Welsh ( 1925) contend that silversides are probably resident throughout the year wherever found. If this be the case for the Upper Laguna Madre, annual production minus emigration and mortality of silversides should be equal to the biomass of the spawning fish. Simmons (personal communication) states that Fish Productwn and Biomass Studies Menidia in the Upper Laguna Madre spawn the year round. 1t has also been shown by Renfro (1958) that this species spawns throughout the year in the Aransas River. There are, however, two spawning peaks, one in late winter and early spring, and another during the summer. A majority of fi.sh over 45 mm standard length were found to be either near or in spawning condition. These larger Menidia were considered to represent production in the study area. Monthly biomass and production estimates are given in Fig. 11, while length fre­ quency data are presented in Fig. 12. -Blouu ---Prod.uction . o . • 2 8. i .:! ,' 1'\ ' 1 1 1 r-......./ \ ' ' ' 1 ' ' ' ' ,' \ ' ' ' ' ' ' : ' "Al'!JJASONDJPlllAlll JJ F1G. 11. Biomass and production estimates for Menidia beryllina from the drop-net quadrat March, 1958-July, 1959. Yearly production may be determined by totaling production for each month. S TANOARD l ENGTH IN MILLI METERS Al'll N 19 6 Sp•c1man$ J9-60mm N ,,, N .fJ 'º '° 'º 'º .... 10 10 ..... I I \¡ -· ~ I - ::, I " I -· "' / .:. I ~ I -· -/ ~ ~ "' -¡ I \;? "'..:.; " :Ji <> ., I I -· ~ -· ¡.> ;. ~ \... - --~ "' - -~ ~ ---~~~~~~~~ru---~~ ..,. 6, ---Call1.nectea eap1dua 6o -Penae1d ahrimp '' '° 4, 40 J' JO I' f ' f ' 2, f ' ' / 1 ' 20 : 1 ' ' 1 l' 1 ' 1 ' 1 10 1 1 ' JASOJIDJPMAMJJ FIG. 13. Total monthly biomass of animals FIG.14. Biomass estimates of the two principal from the drop-net quadrat, compared with gross invertebrates from the quadret drop-net in the oxygen production by plants and temperature, Laguna Madre, March, 1958-July, 1959. March, '1958-July, 1959. a shrimp census. If enough seine hauls had been made to remove ali shrimp from the quadrat each collection, the bottom would have almost surely been disturbed beyond immediate recovery; consequently no effort was made to seine to the "last shrimp." How­ever, as with the fish, many of the shrimp were caught in the first seine hauls and rel­atively' few individuals were taken in subsequent hauls. Three species of penaeid shrimp were present in the drop-net quadrat catch, Penaeus aztecus Ives, P. duorarum Burkenroad, and P. setiferus (Linnaeus). P. aztecus consti­tuted a majority of the shrimp catch. The only species of crab taken was Callinectes sapülus Rathbun. Biomass estimates for C. sapülus are considered to be relatively accurate as all crabs were easily removed from the quadrat by seining. This crustacean was present in the Upper Laguna Madre during every month, and often constituted an appreciable amount of the biomass. Bio­mass estimates for the above invertebrates are given in Fig. 14. Small numbers of Loligo sp. were caught in the drop-net quadrat during September, October, and December. This group of invertebrates was not reported from the Upper Laguna Madre by Simmons ( 1957), and the few individuals captured were probably transient in the area. No effort was made to estímate populations of Ctenophores or Coelenterates. However, visual observations indicated that these groups were well represented in the study area. Summary l. Biomass estimates of fish and larger invertebrates were determined for the upper portion of the Upper Laguna Madre of Texas with a maximum monthly biomass during Fish Productwn and Biomass Studies the summer of 337 pounds per acre (37.8 g/ m2), anda minimum during the winter of 18 pounds per acre (2.0 g/m2). 2. Age and growth determinations were made of the four most abundant fish species, Mugil cephalus, Lagodon rhomboides, Lewstomus xanthurus, and Anchoa mitchilli. 3. The yearly production (total growth of populations during their stay in the area) of all the fishes taken during the study was calculated to be 137 pounds per acre (15.4 g/ m2) . 4. Primary gross plant production was measured using the diumal oxygen method, and is compared with total fish and larger invertebrate biomass graphically in Fig. 13. The annual gross plant production was 4177 g/m2/yr. 5. The efficiency of conversion of gross plant production into fish production on a dry weight basis was calculated to be 0.074 per cent. Acknow ledgments The present study was carried out in the lnstitute ecology program as part of the 1958-59 interagency' contract between the lnstitute of Marine Science and the Texas Game and Fish Commission. The laborious field sampling was made possible by the research assistance of Mr. Emilio H. Guerra, Mr. Neal K. Armstrong, Mr. Jacques Pir­son, Mr. Richard Heimsch, Mr. William R. Olive, and Mr. Ronald Pruitt. The author is particularly grateful to Dr. Howard T. Odum, who initiated the study, served as principal investigator of the contract, and was chairman of the author's grad· uate committee, and to his graduate committee, Dr. Clark Hubbs, Dr. Jack Myers, and Dr. William N. McFarland. The author expresses appreciation to Mr. Howard T. Lee, Mr. Ernest G. Simmons and the staff of the Marine Laboratory of the Texas Game and Fish Commission at Rock­port, and Dr. William N. McFarland, Dr. Carl H. Oppenheimer, Dr. Louis S. Kornicker, Dr. John T. Conover, Dr. Clark Hubbs, Mr. Gonzalo Garza, and Mr. Byung D. Lee of the University of Texas for assistance in many facets of the work. Literature Cited Baker, B. B. 1949. Compilation of salinity data from the Laguna Madre. Texas Game and Fish Comm. Ann. Rept., 1948-1949. Bardach, J. E. 1959. The summer standing crop of fish on a shallow Bermuda reef. Limnol. Oceanogr. 4(1) : 77-85. Baughman, J. L. 1941. Scombriformes, new, rare or little known in Texas waters, with notes on their natural history or distribution. Trans. Tex. Acad. Sci. '24: 14-26. Bayliff, W. H . 1950. The life history of the silverside Menidia menidia (Linnaeus). Chesapeake Biol. Lab,, Pub!. No. 90: 1-27. Bigelow, H. B., and W. W. Welsh. 1925. Fishes of the Gulf of Maine. Bull. U. S. Bur. Fish., Vol. XL, Pt. 1, 1924: 178-18'1. Breuer, J. P. 1957. An ecological study of Baffin and Alazan Bays. Pub!. lnst. Mar. Sci. Univ. Tex. 4(2): 134-155. Broadhead, G. C. 1958. Growth of the black mullet (Mugil cephalus L.) in West and Northwest Florida. State of Fla., Bd. of Cons., Tech. Series No. 25: 1-31. Burr, J. G. 1930. A sail clown the Laguna. Year Book on Texas Conservation of Wildlife '1929­1930, Texas Game Fish and Oyster Comm., Austin, p. 54-58. ' Caldwell, D. K. 1957. The biology and systematics of the pinfish, Lagodon rhomboides (Linnaeus).Bull. Fla. State Mus. 2(6): 1-173. Carlander, K. D. 1956. Appraisal of fish population study-Part 'l. Fish growth rate studies: techniques and role in surveys and management. Trans. 2lst North Amer. Wildlife Conf. 262'-274. Clark, G. L. 1946. Dynamics of production in a marine area. Ecol. Monographs 16(4): 323-'334. Collier, A., and J. W. Hedgpeth. 1950. An introduction to the hydrography of tidal waters of Texas. Publ. Inst. Mar. -Sci. Univ. Tex. 1 (2) : 121-194. Dai:nell, R.M. 1959. Food habits of fishes and larger invertebrates of Lake Pontchartrain, Louisiana, an estuarine community. Publ. Inst. Mar. Sci. Univ. Tex. 5(1958) : 353-416. Dawson, C. E. 1958. A study of the biology and life history of the spot, Leiostomus xanthurus Lacepede with special reference to South Carolina. Contr. Bears Bluff Lab. 28: 1--48. Ginsburg, I, 1952. Flounders of the genus Paralichthys and related genera in American waters. Fish. Bull., Fish and Wildlife Serv. 52 (71) : 266--351. Guest, W. C., and G. Gunter. '1958. The sea trout or weakfishes of the Gulf of Mexico. Gulf States Mar. Fish. Comm., Tech. Sum. No. 1: 1-40. Gunter, G. ·1938. Seasonal variations in abundance of certain estuarine and marine fishes in Louisiana, with particular reference to life histories. Eco l. Monographs 8: '313-346. ----. 1941. Relative numbers of shallow water fishes of the northern Gulf of Mexico, with sorne records of rare fishes from the Texas coast. Amer. Midl. Nat. 26 ( 1) : 194-200. ----. 1945a. Sorne characteristics of ocean waters and the Laguna Madre. Texas Game and Fish 3(1): 7, 19, '21, Z2. ----. 1945b. Studies on marine fishes of Texas. Publ. lnst. Mar. Sci. Univ. Tex. 1 ('l) : 1-190. Harvey, H. W. 195-0. On the production of living matter in the sea off Plymouth. J. Mar. biol. Assn. U.K. 29: 97-137. Hayne, D. W., and R. C. Ball. 1956. Benthic productivity as influenced by fish predation. Limnol. Oceanogr. 1(3): 162-175. Hedgpeth, J. W. 1947. The Laguna Madre of Texas. Trans. l2th N. Amer. Wildl. Conf. 364-380. ----. 1953. An introduction to the zoogeography of the North-western Gulf of Mexico with reference to the invertebrate fauna. Publ. Inst. Mar. Sci. Univ. Tex. 3.(1) : 109-224. Hellier, T. R., Jr. 1957. The fishes of the Santa Fe River system. Unpublished MS thesis, Univ. of Fla. 99 p. ----. 1959. The drop-net quadrat, a new population sampling device. Pub!. Inst. Mar. Sci. Univ. Tex. 5(1958): 165-168. ----. 1961. Fish production studies in relation to photosynthesis in the Laguna Madre of Texas. Ph.D. dissertation. Univ. of Texas, 62 p. Hile, Ralph. '1948. A nomograph for the computation of the growth of fish from scale measurements. Trans. Am. Fish. Soc. 81: 69-77. Hildebrand, H. H. 1954. A study of the fauna of the brown shrimp (Penaeus aztecus Ives) grounds in the Western Gulf of Mexico. Pub!. Inst. Mar. Sci. Univ. Tex. 3(2): 1-366. Hildebrand, S. F., and L. E. Cable. 1938. Further notes on the development and life history of sorne teleosts at Beaufort, N. C. Bull. U. S. Bur. Fish. 48: 505-642. Joseph, E. B., and R. W. Y erger. 1956. The fishes of Alligator Harbor, Florida, with notes on their natural history. Fla. Sta te Univ. Studies Z2: ll'l-156. Kendall, W. C. 1902. Notes on the silversides of the genus Menidia of the East Coast of the United 'States with descriptions of two new subspecies. Rept., U. S. Comm. Fish. 1901: 24I-267. Kilby, J. D. 1949. A preliminary report on the young striped mullet (Mugil cephalus Linnaeus) in two Gulf coastal areas of Florida. Quart. J. Fla. Acad. Sci. 12('1): 7-23. ----. 1956. The fishes of two gulf coastal marsh areas of Florida. Tulane Stud. Zoo!. 2(8) : '175-247. Margetts, A. R., and S. J. Holt. 1948 . . The effect of the 1939-1945 war on the English North Sea trawl fisheries. Rapp. Cons. Explor. Mer. 122': 26--46. McLane, W. M. 1955. The fishes of the St. Johns River system. Unpublished doctoral dissertation, Univ. of Fla., v-361 p. Merriman, D., and H. E. Warfel. 1948. Studies on the marine resources of Southern New England. VII. Analysis of a fish population. Bull. Bingham oceanogr. Coll. 11 ( 4) : 131-163. Nelson, P. R. 1958. Relationship between rate of photosynthesis and growth of juvenile red salmon. Science 128 ( 33'17) : 205-206. Odum, H. T. 1956. Primary production in flowing waters. Limnol. Oceanogr. 1(2): '102-117. Odum, H. T., P. Burkholder, and J. Rivero. 1959. Measurements of productivity of turtle grass flats, reefs. and the 'Bahía Fosforescente of Southern Puerto Rico. Pub!. Inst. Mar. Sci. Univ. Tex. 6: 159-170. Odum, H. T., and C. M. Hoskin. 1959. Comparative studies on the metabolism of marine waters. Pub!. Inst. Mar. Sci. Univ. Tex. 5(1958) : 16--46. Odum, H. T., W. McConnell and W Abbott. 1959. The chlorophyll "A" of communities. Pub!. Inst. Mar. Sci. Univ. Tex. 5(1958): 65-96. Fish Productwn and Biomass Studies Odum, H. T., and E. P . Odum. 1955. Trophic structure and productivity oí a windward coral reeí community on Eniwetok Atoll. Ecol. Monographs 25(3): 291-320. Odum, H. T., and R. Wilson. 1962. Further studies on reaeration and metabolism in Texas Bays, 1958-1960. Publ. lnsL Mar. Sci. Univ. Tex. 8: 23-55. Pearson, J. G. 1929. Natural history and conservation oí the redfish and other sciaenids oí the Texas coast. Bull. U. S. Bur. Fish. 44 (1928): 129-214. Renfro, W. C. 1958. The effect of salinity on the distribution of fishes in the Aransas River. Un­published M.A. thesis, Univ. of Texas, 49 p. Reíd, G. K. 1954. An ecological study of the Gulf of Mexico fishes, in the vicintiy of Cedar Key, Florida. Bull. Mar. Sci., Gulf Carib. 4 (1) : 1-94. ----. 1955. A summer study of the biology and ecology of East Bay, Texas. Part 11. The fish fauna of East Bay, the Gulf beach, and summary. Tex. J. Sci. 7 (4): 430-453. ----. 1956. Ecological investigations in a disturbed Texas coastal estuary. Tex. J. Sci. 8(3): 296-327. ----. 1957. Biologic and hydrographic adjustment in a disturbed Gulf coast estuary. Limnol. Oceanogr. 2('3): 198-212. Riley, G. A. 1955. Review of the oceanography of Long Island Sound. Papers Mar. Biol. Oceanogr., Suppl. to Vol. 3 oí Deep-Sea Research, p. 224--238. Ryther, J. H. '1954. The ecology of phytoplankton blooms in Moriches Bay and Great South Bay, Long Island, New York. Biol. Bull., Woods Hole 106: 198-209. Simmons, E. G. 1957. An ecological survey of the Upper 'Laguna Madre of Texas. Publ. lnst. Mar. Sci. Univ. Tex. 4('2) : '156-200. Thompson, J. M. 1950. The effect oí a period of increased legal mínimum length of sea mullet in Western Australia. Austr. J. Mar. Freshw. Res. 1(2) : 199-220. ----. 1951. Growth and habits of the sea mullet, Mugil dobula Gunther in Western Australia. Austr. J. Mar. Freshw. Res. 2('2) : ·193...:225. ----. 1954. The Mugilidae of Australia and adjacent seas. Austr. J. Mar. Freshw. Res. 5(1): 70-131. Townsend, B. C., Jr. 1956. A study of the spot, Leiostomus xanthurus Lacepede, in Alligator Harbor, Florida. Unpublisbed M.S. thesis, Oceanog. lnst., Fla. State Univ. 4·3 p. Further Studies on Reaeration and Metabolism of Texas Bays, 1958-1960' HowARD T. OouM AND RoNALD F. WILSON lnstitute of Marine Science, The University of Texas Port Aransas, Texas Abstract 123 diurna! curves of oxygen were obtained in 1959-QO to further outline the patterns of total photosynthesis and community metabolism of Texas bays. Examples were analyzed with nighttime variations in respiration, with changing reaeration constants, and with post-sunset artifacts in compu­tational graphs. The area-based reaeration constant increased with depth, but the volume based reaeration coefficient was more constant at about 1.2 ppm per hr per 100% deficit. The volume-based constant increased with wind velocity. Peaks in the 4 yr seasonal pattern of metabolism in the grassy upper Laguna Madre were in phase with peaks of insolation with P and R remaining in relatively close balance from 0.5 gm/m2/day in winter to 20 gm/m2/day in summer. Planktonic systems of Corpus Christi hay were equally productive. Metabolism was slight in a winter cold regime and momentarily interrupted in a spring squall line passage. Hexadecanol had little effect on a salt pond, and inorganic fertilization caused increased metabolism temporarily. Metabolism during dredg­ing was unbalanced towards respiration, and a case of high photosynthesis in flood regimes was reported. A very large diurna! oxygen range was reported in an alga! film system with anaerobic nighttime conditions associated with blue-green dominants. Maximum production rates (30-40 gm/m2/day) were found in the clearest hay, the lower Laguna Madre, with values similar to those for sorne Texas sewage ponds indicating the effectiveness of natural, stabilized communities in recycling nutrients. Production measurements inside and outside of enclosures indicated the ability "of turtle grass systems to maintain fairly normal metabolism for weeks following enclosure. Data from a Louisiana Bayou were similar to data from turbid bays of East Texas. Total phosphorus data indicated slightly higher values in hypersaline bays (2-4 mg-atom/m3) than in bays flushed with fresh water (0.S-2.4 mg-atom/m3). The larger bays were equally or more productive than the small sheltered sloughs and harbors of similar depth. Metabolism fluctuated from day to day in a small boat harbor, but conditions remained aerobic. Extinction coefficients were obtained for white light ranging from values typical of Gulf coastal water to those with a 1% compensation point at 0.5 m in turbid bays. Productivities during the summer in the various bays were correlated with clarity. Respiration often exceeded photosynthesis in the back bays where land run-off was more important. For maintaining maximum gross photosynthesis, management measures may be designed for obtaining water clarity and maximum light utilization, for holding stable salinity and nutrient water mass regimes, for conserving well developed bottom communities for holding nutrient cycles, and for controlling bottom depths to intermediate levels (1-2 m) for optimum combinations of light, circulation, and oxygen range. 1 These studies were supported by a contract with the Office of Naval Research NONR 375(11) Project NR 104-435 on the Productivity of Texas Bays. Further Studies on Reaeration and Metabolism Introduction The bays and estuaries along the ocean margins of the world are the frontiers where man's enterprise is now exploring new ways of using the sea. To carry out research, evaluate fertility, appraise pollution, predict biological events, manage production, de­velop resource yields, and farm the vast shallow oceans, one must be able to assay day by day the total photosynthesis and respiratory consumption of these ecosy'stems. Such assay is attempted with the diurna} curve method involving the measurement of oxygen, total carbon dioxide, and other metabolically active constituents through twenty-four hour periods. From such measurements one may seek to compute rates of turnover of chemical cycles, rates of uptake of radioactive substances, productivities, potentials for increased yields of marine products, and metabolic conditions of the hay' systems. In previous papers on the broad, fertile bays of Texas, data were presented indicating the suitability of the diurnal curve method for the determination of gross photosynthesis and total community respiration in Texas waters (Odum and Hoskin, 1959; Park, Hood, and Odum 1958; Bruce and Hood, 1959; Odum, 1960). To further elucidate the nature of total metabolism and reaeration in marine coastal ecosystems, 123 more diurna! curve measurements have been made in special situations, new areas, seasons, and experimental tests. Selected case histories and seasonal patterns are presented in this report in order to interpret the role of depth, light, temperature, turbidity, nutrients, areas, and agitation on production, respiration, and reaeration. Methods Oxygen analyses by the Winkler method were made on water samples collected at frequent intervals through 24-hour periods representing whole functional areas and water masses. Then rates of gross production, respiration, and reaeration were computed. Procedural details on the graphical analysis were presented in a preceding report {Odum and Hoskin, 1958). In other papers variations were described for sorne special situations (Odum, 1956, 1957, 1960; Odum, Burkholder, and Rivero, 1959). Several new refinements concerning the computation of diffusion and respiration are here described. These methods apply in thoroughly mixing shallow waters. Phosphorus analy'ses were made by H. Bruce (Bruce and Hood, 1959) and R. Ward working with C. Oppenheimer using perchloric acid digestions followed by stannous­chloride-ammonium molybdate colorimetry. Field measurements of foot candles were made with a General Electric Golden Crown Exposure Meter, Type PR 3 with an incident light attachment. The manufacturer sup­ plied a foot candle calibration. Under conditions of rough field use, changing tensions on the spring, and other factors, the foot candle data must be considered approximate and relative. Wind velocities were measured in the field with a hand anemometer Model MRF Florite from Bacharach Industrial lnstrument Company, 200 W. Braddock Ave., Pitts­burgh, Pa. CoRRECTIONs FOR CHANGING NIGHTTIME RESPIRATION From studies by Beyers (1962) on microcosms, from data in sorne diurna! curves (Fig. 1 and 2), from diurna! data in Silver Springs (Odum, 1957), and from experi­ments on plant respiration as a function of oxygen content by Gessner and Pannier (1958) it is known that the respiration of oxygen after dark may exceed that just be· fore dawn in many' instances, especially when oxygen content is much higher at sunset than at sunrise. Wherever post-sunset ·respiration is higher than respiration later at night an error in the difiusion computation may be introduced ultimately causing a slight overestimation of of total C()mmunity i:espiration. r;Z:\J 06 00 12 00 18 00 2 400 0.3 Frc. l. Diurna! curve off Hunt's Pier, Rock­port, Texas, in Aransas Bay, July 11-12, 1960; >alinity, 21 %o. This is an unusual curve in which the respiration decreases markedly during the night. The change in rate of nighttime oxygen decrease occurred even though the winds dimin­ished from 18 mph at sunset to 7 mph at sunrise. Recalling the procedure previously outlined in detail (Odum and Hoskin, 1958), one selected two points during the night from the rate of change graph. In the routine pre· viously used the respiration was taken to be constant at both times of night and any difference in the rate of oxygen decrease was attributed and computed in ratio to the difference in per cent saturation of the water at the two times. Since both respiration and the tendency for diffusion out are greatest in the early part of the night ( or tend­ency for diffusi()n inward is minimal), one attributed too much of the observed oxygen Further Studies on Reaeratwn and Metabolism NO 3 ~A' T[ ll WfU10fCAlolOL AVGllST 1• -19,IMO Ht;;CSJ OIOO 1200 llOO UOO ~ ~o. e o o o º·º t--'cr-Af,F . 500 M .' ~ -0. 4 GULF ~-O.e o -1.2: ~ .... F1G. 2. Diurna! curve in a shallow slough (Pond No. 3) after addition of hexadecanol at noon, Aug. '18-19, '1960: salinity 3'3.6%o; wind with little variation through the night 0-6 mph. This curve shows a decrease in respiration during the night. Also included is a map of Port Aransas waterways showing ponds and sloughs: 1, beach pool; 2, shell shop pond; 3, Üppenheimer House pond; 4, ferry road alga! mat; 5, city boat basin, stations a, b, and c. decline at night to diffusion. The diffusion correction was overestimated. When the graphs were finally completed, the nighttime respiration was slightly overestimated and the P / R ratio too low. In aerobic waters the magnitude of error is small judging by the small differences in nighttime oxygen respiration indicated in sources cited above. The large differences in Fig. 1 and 2 are unusual. In anaerobic waters, however, very large differences develop as recently reported (Odum, 1960) in cases in which oxygen consumption although rapid after sunset stops later at night as oxygen runs out. To sorne extent a localized anaerobic effect may always exist where the bottom ooze is in the euphotic zone with declining oxygen metabolism at night. Data by Beyers (1962) on carbon metabolism of severa! types of balanced microcosms show the maximal nocturnal respiration at sunset suggesting a relation to the labile organic matter accumulating from the net production of the previous day. In his graphs respiration declines rapidly, perhaps logarithmically during early night. If the bays are behaving similarly, the diffusion constants obtained in this paper with the simple formula (R constant) are too large, since they include sorne of the change in respiration as change in diffusion. Were the change in respiration during the night between the two computational times known, the 'diffusion constant might be used as k= (q.-qm)-(r.-rm) s. -Sm where k is the volume based diffusion constant, q the rate of change, r the respiration, and S the saturation deficit. Because the data on diurna! pH C02 curves for these hays (Park, Hood, and Odum, 1958) do not yet show systematic trends in nighttime respiration, it seems premature to attempt complex assumptions about respiration for estimating diffusion directly from the diurna! graphs. Thus in this paper the simple procedure has still been used, and the values for diffusion constant may be regarded as upper limits. Ultimately independent physical determinations of the reaeration constant may solve this problem with the night respiration and daytime net photosynthesis deter.mined after subtraction of diffusion as independently deter.mined. In rate graphs analyzed in the previous paper (Odum and Hoskin, 1958) , one line for "R" was drawn through the average nighttime respiration. In many of the graphs after diffusion corrections have been applied, there was observed a greater respiration after dark than before dawn even without the correction of the diffusion constant described above. Where pre-sunrise and post-sunset respiration differ in this paper, a dashed line is connected diagonally connecting dawn respiration rate to the sunset respiration rate on the rate of change graph. This line may be used for counting squares in estimat­ing gross photosynthesis. How real the line may be as an indication of daytime respira­tion is not known. Where the diurna} variation of respiration of oxy'gen is severe as in anaerobic systems, it seems best to use a reaeration ( diffusion) constant that is approximated independently from k's in similar conditions of depth and mixing as measured under aerobic condi­ tions (Fig. 3). For example, k or about 1 gm/m3/hr/100% deficit is representative of the Texas bays under average conditions. After applying the assumed diffusion con­ stant, one may use the corrected rate graph to indicate the course of night respiration. REAERATION CoNSTANTs AND WATER DEPTH In streams the area-based reaeration coefficient increases with the rate of stirring and thus increases with current, wave action depth, and size of the water eddies (Phelps, 1944; O'Connor, 1958; Velz, 1939). Consider reaeration relationship to depth in the bays. Reaeration constants computed by the diurna} curve method for Texas bays have been plotted in Fig. 3 as a function of depth. Reaeration and the variation in re­aeration increase with depth. Although the reaeration computations from diurna} curves are subject to many sources of variation and error, the data show a regression from values of 0.1 gm/m2/hr/100% deficit in shallow water to values greater than 3 gm/m2/ hr/ 100% deficit in the deeper bays. The line in Fig. 3 may be used to estímate reaeration constants where night data are inadequate or where other complexities prevent the usual computation. The volume based reaeration constant (k) in gm/ mª/hr/ 100% deficit is related to the area based constant (K) by the definition: K = zk where z is depth in meters. The regression line for K from Figure 3 was converted into a line for k by dividing by depth as indicated in Fig. 3. The volume based constant is rather independent of depth in these bays. Further Studies on Reaeration and Metabolism 20 30 WINO MPH OEPTH lN METERS F1c. ·3. Reaeration constants on an area basis F1c. 4. Reaeration constants on a volume basis (K in gm/m2/hr/ 100% deficit) as a function of (k in units mg/ l / hr/100% deficit) plotted as a the bottom depth (in meters) . A linear regres­function of average wind velocity during night­sion line is plotted as computed from the data time hours. points. Dashed lines fonn boundaries for 95% confidence. Also plotted is the same regression line expressed as a volume basis (k = K/ z in units mg/l/hr/100% deficit). Each point in this figure was computed from a diurnal curve using changing rates of change at night following the procedure of Odum and Hoskin (1958). Values for reaeration in San Diego hay of about 0.12 gm/ m3/ hr/ 100% deficit (vol· ume base) (O'Connor, 1958) and for the Thames estuary by Gameson and Barrett (1958) of 0.5 gm/ m2/ hr (area base) are within the range in Texas waters on the low si de. REAERATION CoNSTANTS AND WINo VELOCITY Because the passes are narrow and the Gulf tides small there is little tide in most of the bays and most of the stirring action is wind driven due to waves and wind-induced circulation. The reaeration coefficients as computed from the diurna! graphic analyses are plotted for environments of similar depth in Fig. 4 as a function of observed wind velocity during the night lncreasing reaeration coefficients can be observed with in­creasing winds. The graph in Fig. 4 has been used in several instances to compute diflusion corrections on days in which wind velocities varied markedly at different times. Estimates of wind velocity in the field were used to select a reaeration constant for each time of the day·. Computation of reaeration rates from a diurna! graph can only be done if one has two periods with nighttime rate measurements in which wind velocities are fairly similar. Such data are plotted in Fig. 3 and 4. PosT-SUNSET DIFFUSION ARTIFACT In the usual graphic analysis of diurnal curves, after selection or cofi/putation of k, the diffusion correction is applied for each hour of the day and night so that the final rate of change graph indicates only the photosynthetic and respiratory metabolic rates. When no allowance is made for changing constants and where there is a change of re­aeration rate due to wind variation, sorne artifacts are produced. One of these artifacts has been observed frequently, a post-sunset bulge. Where this irregularity is recog­nized it may be allowed for in metabolic computations. Field measurements of wind ve­locity with a hand anemometer are now a standard part of the diurnal procedure. In many' localities on the Texas coast particularly in summer there is a marked sea­breeze-landbreeze eff~t so that the prevailing southeast trades pulse with diurnal vari­ation. The hay· waters are much more vigorously mixed in the evening than in the early morning. There is a resulting diurnal change in the reaeration constant. Because many of the curves pass through saturation about sunset, the error is not great in most in­stances. However, if one uses one reaeration constant uniformly during a night, one introduces an artifact that looks like a burst of post-sunset photosynthesis (Fig. 5 and 6). This graphic artifact develops because one undercorrects for aeration early in the eve­ning and overcorrects later. One may' suspect this effect whenever the post-sunset oxygen curve is concave downward. To avoid the effect one may use a different k in the early evening from that used later at night using wind observations and Fig. 4 to estímate a suitable k. Results In the paragraphs that follow photosy'nthetic and respiratory data are presented for several situations and seasons with an interpretive emphasis on the special features discussed in each case as a natural experiment. P is gross production; R is total com­munity respiration. The various new refinements in analysis of these graphs have been applied to older data wherever used in this paper so that the values in Fig. 7 may not be exactly the same as previously puhlished in sorne instances. In presenting diurnal data from a 24 hour series, all items are arranged with noon in the middle of the graph even though the series began at any time of the day. The right side of the graph may be earlier in time than the left side. The time of start is indicated by a break in the line connecting the points. One should not compute a rate of change for the segment connecting the start to the end, as such a segment is not real. One may connect the points on the rate graph across such a gap in order to compute photosynthetic areas without affecting values appreciably·. SEASONAL CYCLES IN THE LAGUNA MADRE, A TmN-GRAss SYSTEM With the help of many persons and as part of several related studies, diurnal curve measurements have now been made in the Laguna Madre over a period of 4 years in­cluding dry and wet years. The measurements in the first year were made in a slightly more inshore station inside Pita island than in later years when the curves were taken outside of Pita island. Data on photosynthesis, respiration, computed diffusion con­stants, salinity and temperature are reported in Fig. 7. LAGUNA MADRE PORT 1 SABEL (STATION 1) AUGUST 8 -9,19 6 0 ~··:LZ:sJ 240 z o ¡:: o: "' 1­ " "' "' ... o o: ~ ~ O' "' " .., PORT BAY BRIOGE, COPANO BAY JULY 11-12.1960 "'z >: "' u ... o .., 1­ o: "' F1 ú 1 0600 1200 1eoo 2400 WINO MPH F1G. 5. Diurna! curve showing the post-sunset bulge artifact due to decreasing winds and aera­tion after dark frequently found in Texas due to seabreeze effects. Grass flats in the Lower Laguna Madre at Port Isabel, 1.4 m, salinity 36.7%0, wind velocities in mph. 1.0 o: "' ...J o.• ON ,. "' .., o.o +---+----,-=4§.;;.;.;4*.---t--oc.+----.j z "' " u "' i... -0.4 o .., 1­ o: " 0600 1200 1800 2400 F1c. 6. Diurna! curve with post-sunset bulge artifact in Port hay, a low salinity arm of Copano Bay receiving Aransas River. Depth 0.92 m; sa­linity 13.6 %0, July 11-1'2, 1960. /NDIAN POINT P IER JUNE 29-30, 1960 I cr '!: 0.3 I ~ o" 0.2 "' "' o.o z IL o -0.2 .... "' =--~--~---< sº-~~------------------~ ;} oz ~ i ~ ~oot--~~"""¡¡;¡;¡¡;¡¡;¡;;;;;;;:¡~----!1----if-cf':'-" ~ lt•t. 7 CU•1"W21QAT-l.\­ . s:. 1 NOIAN POINT PIER JUNE 23, 1960 (OEPTH 3MI ::~ STRONQ WINO :}=:-::01 PARAOISE PIER (OEPTH 82 CM) JU NE 23, 1960 z o .... "" ::> "' .... ;:\ .. ~ 1~000....-~~~~~~~~~~~~~~----. ... ..J o z u "" .... ~ 4,000 .... :r ~ ..J 0600 1200 1800 Z400 •o :r o. ::.--,..---' " zo TROPICAL o z STORN ii 0600 1200 1800 2400 Frc. 12. Diurna! curves at two stations in Corpus Christi hay June 23, '1960, as a tropical storm approached, accelerating winds, and lower­ing heavy clouds. This is an example of the effect of an increasing reaeration rate during the course of the day. HAYTERS BOAT BASIN JULY 2S-26, 19'9 ~ 7~ION a 1l. KONE STAT 0 0 ... o o"' . o " . ·~~~~.....-~~~.....-~~~--,---~~~~ STATIOfil 7 ::E--:::-:4 ::±:4 OIOO ltOO 1100 t400 F1c. 13. Diurna! curves taken by Miss Ger­trude Kone in a new small boat haibor, Port Aransas, Texas, July 2!J-:26, 1959. Clear circles are surface samples ; solid circles are bottom samples. See Fig. 2 for map showing stations a, b, and c. 10 5 00 6 12 18 TI ME ºº F1c. 14. Diurna! curves for the Oppenheimer House Slough before and after fertilization with nitrogen-phosphorus fertilizer. See Fig. 2, pond No. 3. blowing polar air over bays 0.5 to 1 m deep there was a rapid fall of temperature of the water, corresponding increase in saturation capacity of the water, and influx of oxygen by diffusion. Under conditions of rapid diffusion due to wind agitation, conditions are not optima! for application of the diurna! curve methods. Nevertheless when the diffu­sion correction was applied in the usual manner and the oxygen that had diffused in was removed from the rate of change curve (Fig. 4) , a definite though small photosynthesis was found. Even though temperature changes are large and rapid in the bays in winter, the metabolism and photosynthesis of the c<>mmunitties does continue. Sorne acclimation is suggested by the greater respiration the second day. During the same period a 24 hour dark-light experiment was run in triplicate with bot­ Further Studies on Reaeratwn and Metabolism tles at surface and bottom. On an area basis plankton metabolism estimated from bottles was 0.28 gm/m2/ day respiration and 0.49 gm/m2/ day gross photosynthesis. As in previous comparisons of bottle and freewater data, higher values in the freewater indicate importance of bottom components (Odum and Hoskin, 1958). COMPARISON OF METABOLISM ON SUCCESSIVE CLEAR DAYS AND CLOUDY DAYS In the Thalassia-Diplanthera grass of Redfish hay diurna! curves were taken for a pair of successive clear and coludy days in winter, January 31-February 1, 1957, and for a pair of successive clear and cloudy days in summer, August 10-11 and August 13-14, 1960. The data in Table 1 indicate a very large range in photosynthesis from day' to day correlated with cloudiness. In winter the sunny day was 50% more productive: (clear day, P = 6.3 gm/m2/day; overcast day, P = 3.9 gm/ m2/day); in the summer ex­ample 4 times more productive; (clear day, 10,000 foot candles at noon, P = 38.5, R = 33.0 gm/ m2/ day; cloudy day, 3,000 foot candles at noon, P = 8.5, R = 7.9 gm/m2/day). Apparently the respiration was a function of the photosynthesis since it diminished on the cloudy day. Beyers (1962) found a close correspondence between community respiration and community· photosynthesis in microcosms from day to day, P depending on the preceding R and vice versa. METABOLISM DuRING APPROACH OF A TROPICAL STORM On June 23, 1960 a diurna! curve was obtained at two stations in Corpus Christi Bay as a tropical storm moved in. Data are presented in Fig. 12 and diurna! computation madc cin the mean curve. The winds increased from early morning at 5 mph to 40 mph by sunset occompanied by lowering ceilings and heavy rain. Reaeration was maximal by evening with waters swirling around the hay' at a great velocity in water about 3 m deep. By evening the changing reaeration constant was 2 to 3. In spite of the tremendous reaeration rate, the oxygen remained in equilibrium below saturation presumably due to increasing respiration. The computed respiration rate necessary to balance reaeration was higher than usual for Corpus Christi Bay as might be consistent with high tempera­ture, extensive agitation, and resuspension of hay bottom materials under maximum winds. The photosynthesis was measurable in the morning while the light intensity was appreciable before the onset of heavy afternoon clouds. The analysis of this curve is an example of use of the diurna! methods in a complex situation. Complex analysis cannot yet be turned over completely to routine assay. METABOLISM IN A SMALL BoAT HARBOR In spring, 1959, a small boat harbor was dredged into the land of the bar island at Port Aransas producing a stagnant arm of the sea about 4 m deep, 30 m wide, and 300 m long (Fig. 2). Shortly after its formation in summer diurna! curves were run for 3 sta­tions (Fig. 2: a, b and c) in this body by Miss Gertrude Kone as part of course re· quirement of General Marine Science with the results in Fig. 13. Data from the deeper of two sampling levels indicated a greater respiration than at the surface level, although stratification was not sharp. Computation of production was made with the mean of top and bottom samples. After a year of heavy use by small boats, curves were again analyzed for the summer of 1960 with the results in Table l. The use by the boats, fuel leakages, and other lo· calized pollutions had apparently no great e:ffect at that time. In spite of the considerable metabolism and sheltered nature of the basin, anaerobic conditions did not develop. There was considerable range in metabolism from day to day (1.4-18 gm/m2/ day). METABOLISM OF SLOUGHS On the margins of the bays are small hollows, depressions, and pools at intertidal Ievel containing 0.1 to 1 m of water. Sorne of these are connected with the main water body; others are isolated from normal water exchange. A series of measurements of metabolism was made in these sloughs. These bodies generally lack the strong circulation of the wind driven motion of the broad days of similar depth, but sorne have special lo­calized sources of nutrients from pollutions, limd drainage, or other cause. Diurna! curves were run on sorne of these sloughs as reported in Fig. 2, 14-16, and Table l. Whereas the daily range of oxygen was maximal in these bodies because ali of the metabolism was compressed into a very thin layer, with the exception of the shell shop pond, the total metabolism per area (3-9 gm/ m2/ day) was notas great as in sorne of the larger bays that were better mixed and less disturbed such as Redfish Bay and Laguna Madre. Ali intertidal waters tended to be subjected to catastrophic drying during ex· tremely low sets of the Gulf when water drained out of the bays for several days. Turbid flooding occurried at high tides, and fresh water flooded in during heavy rains. During the period the shell shop pond was receiving fish o:ffal and domestic pollution. Photosynthesis and respiration rates of that slough were greater than in the other lit. toral waters measured (5-15 gm/m2/day, Table l). FERTILIZATION IN SLOUGHS ·In Fig. 14 are graphs for Oppenheimer House Pond, a small slough in which 50 pounds of nitrogen and phosphorus fertilizer powders were added July 18, 1960. As in other fertilization work in fish ponds, there was an immediate stimulation of photosyn­thesis (Table 1). Apparently the concentration of trace nutrients being maintained by the interna! P-R cycle in the slough was less than the new concentrations which devel­oped when the fertilizer was added. Subsequent measurements indicated a reurn to pre­fertilization values by the end of August a month later (Table 1). Respiration values fol. lowed photosynthesis values. METABOLISM IN A WATER FILM SYSTEM One of the important ecosystems of the south Texas hay margins is the blue-green alga! mat growing in films of water about 10 cm in depth. Diurnal curves in such sys­tems as in the example in Fig. 15 provide sorne insight as to the kind of environment and productivity. In spite of the extreme shallowness of the water, the range of oxygen was tremendous from anaerobic conditions to 240 per cent supersaturations in the course of the day. Contrary to expectations based on the theory that shallow waters are well aerated, the aeration is less e:ffective in moderating the metabolism in the film community than in deeper systems. The action of metabolism tends to be concentrated in such EXPERIMENTAL POND (DEPTH 13 CM) JULY 18-19, 1960 ..• ...------------,..,.~-------, _ Bl :::: ·~ Mi:~ "' "' "' "'z ~ u ... o "'.... : -2 .1 12poo "' "'..J o z u "' .... o o 4POO ... .... e :::; f\ 0600 1200 1000 2400 2 100 .. ~ :i:: .... ¡: 1 z "-1 ~ LIGHT TRANSMISSI ON Fic. 15. Diurna! curve in a very shallow slough with 13 cm water over a benthic alga! film community, along Ferry road, Port Aransas, July 18-19, 1960, salinity 39.6 %0, wind 3-10 mph, uniform during period. See Fig. 2, No. 4. a thin layer that diurna! changes are very large. The reaeration constant, on the other hand, on an area basis diminishes with depth (Fig. 3). In the example in Fig. 15, K is 0.25 gm/ m2/ hr/ lOO%, and areation does not keep up with the wild swings of the concentrations in the film. For example just before noon, clouds diminished the light intensity as recorded in a drop from 10,000 to 6,000 foot candles. As instantaneous and marked drop in oxygen content occurred ( Fig. 15). lt may be postulated that the reason for the dominance of the blue green algal mats in waters at 10 cm and not at greater depths is the anaerobic nighttime period in the film systems. Apparently the shallowest systems in the Texas bays are the only natural communities which regularly go anaerobic at night. The blue-greens survive. The temperatures may also have a role in causing unusual biota. The diurna! range of temperature from 27 to 39ºC in the very shallow waters and the wide fluctuation of oxygen contents tends to eliminate most consumer species thus favoring a net deposit of organic matter. The possible role of the alga! mats in organic sedimentation has been already discussed (Fisk, 1959). HEXADECANOL ExPERIMENT IN A SLOUGH Twelve pounds of hexadecanol were broadcast by hand on August lí, 1960, on water and marginal muds of each of two slough ponds (Fig. 2: Oppenheimer House Pond (No. 3) and Shell Shop Pond (No. 2) after diurna! curves had been made previously. Surface water ripples were visibly damped as the material was cast on the water in flakes, but by the end of the 24 hour period there was no sign of the hexadecanol over the water and the ripples were back to normal. Metabolic values were not markedly changed al­though there was possibly sorne increase in respiration over photosynthesis (Fig. 2 and Table 1). Harris and Meinke (1960) also reported an increase of bacteria! action in sedi­ments of fresh waters receiving hexadecanol due to metabolism of the solid alcohol ma· terial by the bacteria. METABOLIC RATES OF SEWAGE PoNDS During World War II the Texas State Health Department made sorne studies of oxy­ gen in experimental sewage lagoons. Sorne of these data were made available for the purpose of computing the total production and respiration. The data were derived from an unpublished report prepared by V.M. Ehlers, T. W. Ray, and E. C. Nelson in 1949. The pond on the average was O.75 m in depth, 41 m long, and 2.4 m wide. Supple­mentary lights were provided at one end. Sorne difference in oxygen values were found with about 1-4 ppm more oxygen in the lighted end. In recomputing the graphs for pur­pose of comparison with the natural bays, the data for the two ends of the long lagoon were averaged as presented in one series in Fig. 16. As included in Table 1 production ranged from 14 to 46 gm/ m2/day with respiration in a similar range. P exceeded R in 3 of the diurna! curves but R was in excess in the fourth. 1 REsPIRATION ExcEss IN BACK BAYS The back bays extending away from the beach line and receiving rivers developed respiration in excess of photosynthesis (Table 4; Fig. 1, 6, 17 and 18) suggesting a con­sumption of organic matter from an imported or previously stored source. R was greater Further Studies on Reaeration and Metabolism SABINE LAKE PORT ARTHUR (OEPTH 2M) JUNE 27, 1960 ::~:e;;~ SEWAGE L AGOON SA MARCOS AIR BASE JULY 20,19 46 EHLERS, RAY, MELSON a: ¡;;¡:~ 1.1.J 0600 1200 1800 2 4 00 ,_ " a: F1c. 16. Diurna! oxygen curYe in a freshwater sewage lagoon, San l\Iarcos, Texas, July 20, 1938. Data from Ehlers, Ray and Nelson. Depth 0.75 m: P, 21 gm/ m2/day ; R, '25 gm/ m2/day. K= 1.05 gm/ m2/100% deficit. than P at times of high turbidity both in low salinity conditions and in very high salinity conditions. Note frequent low P / R ratios for Baffin, Sabine, Lavaca, Corpus Christi, Copano and San Antonio Bays (Table 1). Baflin Bay is in a very arid area and was ob­serwd with an excess of respiration over photosynthesis for extended periods. The hay was continuously turbid suggesting a runoff of organic matter after cloudbursts over the arid lands of the surrounding King Ranch, little-covered with vegetation. Whereas the rains coming in floods were not frequent enough to equal evaporation, runoff was apparently adequate to supply the hay with enough particulate or other organic matter to maintain consumption in excess of photosynthesis. Upper areas of San Antonio Bay at low salinity were observed with low P /R ratios near the hay delta of the Guadalupe River on two occasions also (Table 1). The Louisi­ana Bayou curves cited in a later paragraph are similar. METABOLISM AFTER FLooos In 1960 a major flood developed in the Port Lavaca area with 15 inches rain causing the salinity of the arms of the Matagorda hay to fall to oligohaline amounts (less than 1 ~('.0). A diurnal curve measured in the headwater area during the flood runoff is pre­sented in Fig. 19. Photosynthesis exceeded respiration. lt is rather remarkable that pho­tosynthesis was relatively high immediately after so sudden an upset. Apparently there are not always excesses in respiration in the runoffs. The quick recovery of the head­water producers was further established by Siler and Odum in an experimental pond microcosm with oysters and low salinity waters in which flooding rain waters were in­troduced. Photosynthesis returned to normal in several days. HYNES BAY AUSTWELL (OE PTH 46CM) JULY 11·12, 1960 o: ~ ~ o"' 2 "' w "'z :z: "' u "­ º w .... o:"' 14,000 w "' ..J o z u "' .... o o "­ .... 4,000 :z: "'::¡ LAVACA BAY CAUSEWAY BRIDGE (DEPTH 1.68Ml JULY 14-15,1960 o: ~ ~ o"' "' 2 w z "' :z: "' u "­ o w .... "' o: -o.• 0600 1200 1100 2400 FH:. 19. Diurna! curve from causeway bridge Frc. 18. Diurna! curve for Hynes Bay in San in Lavaca Bay showing metabolism after a fiood, Antonio Bay, Texas, July 11-12, 1960. 'Salinity July 14-15, 1960. Salinity 1.1 %0, depth 1.7 m ; 1.8 %0 ; depth 0.46 m; wind '12 to 15 mph in wind 12-'14 mph in the afternoon diminishing to afternoon, O to 5 mph later at night. calm in the morning. METABOLISM AFTER DREDGING IN REDFISH BAY (Turtle Grass) Another kind of inflow of turbid matter containing organic substrates occurred as a result of dredging of an intra-coastal channel near Redfish hay. Two diurna) curves were made during the dredging while the clouds of turbid water were drifting over the stations. The first off Bishop Pier in 2 m water March 10-11, 1959, at salinity 18.2 %o produced values: P, 3.0 gm/ m2/ day and R, 12.4 gm/ m2/ day. The second curve near Ransom island in 1 m depth Aug. 5-6, 1959, over grass flats at salinity 29.8 %o yielded values, P, 13.6 gm/m2/day and R, 17.3 gm/m2/day. Thus in both cases respiration much exceeded photosynthesis during the dredgings. After the dredging a light )ayer of silt was deposited over the turtle grass flats as described elsewhere (Hellier and Kornicker, 1962). lt is apparent that respiration ex­ceeded photosynthesis, possibly due to the consumption of organic matter added with the spoil sediments. The photosynthesis was not much diminished during or after dredging as compared Further Studies on Reaeration and Metabolism with data from a previous year. The additional respiration due to extra organic matter did not apparently interfere with normal production. High production and dense grass found after dredging may have resulted from release of nutrients. METABOLISM IN AN ENCLOSURE OVER TuRTLE GRASS In Redfish Bay in June 1958 a fiber glass enclosure was constructed with 3 fiber glass sheets each 3 m long arranged in a triangle so as to make a tank. This enclosure was set over the turtle grass beds in 0.5 m depth at station 2 in Redfish hay. On June 10 a diurna! curve was run on the inside and on the outside. The mean curves are similar as indicated in Fig. 20. Metabolism was similar outside the enclosure (P, 6.4 gm/ m2/ day; R, 11.8 REOFISH BAY STATIONS 1-2-3-4-& (DEPTH 13 lNCHES) JULY 7-8, 19 &1 REOFISH BAY STATION 2 (OEPTH 0.~2M) JUNE 10, 19~9 10.,--~~~~~~~~~~~~~~ OUTSIOE TRIANjGLE 0 I •, o I ' I ' O ¡· o \ 1 / A \ / '\ 1 /it , ,,..,,,." o\ , I ' 'I ' I \ '\ INSIOE TRIANGlE 0600 1200 1800 2400 .... 0000 IZOO 1000 F1c. 20. Diurna! curves over turtle grass beds in Redfish Bay inside and outside a fiberglass F1c. 21. Diurna! curves over turtle grass beds enclosure, June 10, 1959. Salinity, 28 %0 ; depth in Redfish Bay inside a fiberglass enclosure and 0.5 m. Computations based on the inside curve in 5 outside stations July 7-8, 1959. In this figure yield: P, 5.9 gm/m2/day; R, 11.1 gm/m2/day. each point is the mean of two separate Winkler Computations from the outside curve are: P, analyses. Salinity, 3·2.8 %0. 6.4 gm/ m2/ day ; R, 11.8 gm/ m2/ day. gm/m2/ day) to that inside the enclosure (P, 5.9 gm/ m2/ day; R, 11.1 gm/ m2/ day). The graph for the outside water was slightly more irregular probably due to sorne heterogeneity of water drifting over the flats. Respiration exceeded gross photosynthesis on this day as throughout the season following the first dredging in March that released a light layer of turbid materials into the grassy areas. During this period the wind ranged from 5 to 18 miles per hour. Later on July 7 during a period of extreme shallow water (0.3 m) in spite of diffi­culties in getting into the hay, measurements were taken at 5 hay stations and again in the enclosure. The data are indicated in Fig. 21 with each point based on duplicate samples. A computation for the whole hay based on the mean of all the data indicated a gross production of 13.8 gm/m2/day and respiration 12.3 gm/m2/day. The grass beds were prostrate preventing appreciable circulation. Temperatures in the afternoon reached 33-36°C. Oxygen levels were slightly lower in the enclosure especially at dawn indicating a slightly greater respiration relative to photosynthesis in the enclosure at this time, although production levels were still high. These results indicate that enclosures can be placed over turtle grass beds for experi­mental purposes without immediately upsetting community metabolism. Further Studies on Reaeration and Metabolism LOWER LAGUNA MADRE, PORT ISAS EL AUGUST 8-9, 1960 O STA. 1 • e ITA. Z SAN ANTONIO BAY JUL Y 11-12, 1960 2 .0 a STA. 3 2.0,....----------------,• o o •o o a: o :e • .. 1.0' a: 1.0 z z ~ o .. "'z 'z .. o 1 • o.o . o.o • • b ~ • -0 .5 -0.4 S,000 10,000 5,000 10,000 LIGHT -FOOT CANOLES LIGHT-FOOT CANOLES Frc. 22. Gross production as a function of light intensity in foot candles including data from different times of day. The left figure was taken from a grassy, relatively clear bay, Lower Laguna Madre, Aug. 8-9, 1960; the right figure was taken from a more turbid hay, San Antonio hay, July 11-12, 1960 : solicl circles, Hynes Landing; crosses, Gonzalez camp. METABOLISM IN A LouisrANA BAYOU A pair of diurna} curves were made during sunny weather in a low salinity bayou at Hopedale, Louisiana, April 21, 1960 prior to dredging of the Mississippi River by-pass channel. The water in this area slides back and forth with the tide through small brackish lakes and channels among islands of marsh grass. One curve was taken at the margin of open water of Lake Borgne at about 1 %o and the other in Hopedale slightly more seaward at high salinity of 5-6 %0• The oxygen change diurnally was very slight in both curves. Although the graphs were not as regular as those in more homo­geneously mixed bays, there can be no doubt about the small amplitude of the metabo­. lism. Computing metabolism for an average depth of 2 m, gross photosynthesis values found were 1.8 and 2.6 gm/m2/ day; respiration values were 3.8 and 2.4 gm/m2/day. The waters were turbid with detritus from the marshes. The conditions were apparently similar to those extensively° studied at the University of Georgia Marine Laboratory in which metabolism in the water was much less than that of the above-water marshes and dependent upon it (Ragotzkie, 1959). Discussion From the case histories presented in the previous section one may draw sorne in­ferences about the role of environmental factors in controlling the overall metabolism of estuarine ecosystems. THE ROLE OF LIGHT, EFFICIENCY The close correspondence between the diurna! variation in light and the diurna! varia­tion in photosynthesis was illustrated in the previous paper (Odum and Hoskin, 1958). Further Studies on Reaerati.on and Metabolism Further evidence may be found in the 123 additional diurna} curves of photosynthesis, which have the general hump shape of the incident light. The sequence of productivity during passage of the clouded cold frontal zone during a time of relatively high pro­ductivity in May (Fig. 10) and the sequence of productivity on successive clear and cloudy days further indicate the close correspondence of oxy'gen production as measured in the free water and the incident light energy. To further analyze the relationship of hay photosynthesis to hay light intensity, graphs were drawn of hourly photosynthesis as a function of light intensity as measured with a General Electric exposure meter with a foot-candle scale in the field (Fig. 22). The increase of efficiency with decrease of light intensity familiar in physiological studies of single plants is again verified as characteristic of whole ecosy'stems ( Odum, McConnell, and Abbott, 1958). As discussed in the previous paper, as implied from free water data discussed by Verduin (1957), and as found in microcosm studies by Beyers (1961) the efficiencies in the morning are somewhat higher than in the late afternoon. This may be due to the diminishing nutrients available late in the day as demonstrated for phosphorus in these same bays by Bruce and Hood (1959). Although one might expect a sewage lagoon (Fig. 16) with high nutrient levels to at­tain maximum possible efficiency in utilization of light, it may be noted that the natural and unpolluted grass flat systems of the Laguna Madre (Table 1 and Fig. 5, 7, 20, 21 and 22) have metabolism as high as the sewage lagoons. Where gross photosynthesis reaches a maximum at about 40 gm/ m2/ day in either a grass flat or sewage lagoon in south Texas in summer, the efficiency of utilization of light energy in available wave lengths is about 6%, based on usable incident radiation of 2850 kg/cal and an approximate conversion of 4 kg-cal/gm oxygen metabolized. Thus both the man made system which was started with abundant nutrients and the natural system that accumulated its own necessary nutrients in a system of geochemical recycling were equally efficient. These efficiencies are similar to those attained in other communities of maximum output else­where in the world, the coral reefs, the agriculture of maximum fertilization, the rain forest, the Silver Springs system and others (Odum and Odum, 1960). Since the photosynthetic output is dependent on incident light reaching the plant cells, the amount of absorption and scattering by turbid materials and water controls the productivity. The higher yields of the relatively clear front bays as compared to the turbid back bays may be related to differences in light energy' reaching plant cells. Note photosynthesis at the same light intensity comparing the lower Laguna and San Antonio hay (Fig. 22). In Fig. 23 are plotted representative graphs of penetration of light with depth. In the very turbid back bays such as Baffin and Copano hay the hay bottoms, although shallow, are illuminated with less than 1 % of surface light intensity. The very clear lower Laguna al lows more light penetration than Gulf waters at times. For plankton systems importance of the depth of the mixing layer as compared to the depth of light penetration ( euphotic zone) was quantitatively described by· Sverdrup (1953) and applied to conditions in turbid estuaries at Sapelo island by Ragotzkie (1959). Where the depth of mixing is great enough to carry the plankton cells into the shade too long for cell photosynthesis to exceed cell attrition, the phytoplankton popula­ tion cannot survive. The layer is said to be below critica] depth. Thus, as waters get deeper, photosynthesis of the grassy-algal bottoms is replaced with a phytoplankton sys­ TRANSN ISSlON Frc. 23. Percent of surface visible light reaching bottom of Texas bays as a function of depth. tem, and finally may practically disappear in turbid waters. Murphy (1962) has pro­vided a graph quantitatively relating turbidity and depth according to the quantitative predictions of this theory. Where the bottom is within the euphotic zone, high productivities are possible even with high turbidities. Waters circulating from deeper zones may not gain in net produc­tion except while they are passing over shallow bars. Under such circumstances the pro­duction of the whole hay may be a function of the ratio of area shallower than the criti­ca! depth to the area deeper than the critica! depth. Whereas turbidity is not disastrous in the shallow depths, it may essentially eliminate photosynthesis in the deeper waters. Fortunately, most of the bays of Texas are shallow enough and productive enough to be above the critical point much of the time. The first objective of any program for stimulating greater prirnary production in deeper Texas bays should be elirnination of sources of turbidity. THE ROLE OF TEMPERATURE AND COMMUNITY REGULATION In the Texas bays both light and temperature undergo large annual and day to day variations between surnrner rnaxirna and winter rninima (Fig. 7). In Silver Springs, Florida, at constant temperature it was possible to attribute all of the annual range of photosynthetic production to the variation in incident light, but in the Texas bays sorne authors have been tempted to attribute sorne of the winter decline in biological stocks and activity to the decrease in ternperature. What evidence there is, however, suggests a rninor role for ternperature. Low ternperature (above freezing) does not in itself pre­clude high production rates. The basic photosynthetic process is not ternperature de­pendent although ternperature affects the output of whole plants studied (Stafelt, 1960). Further Studies on Reaeratwn and Metabolism High rates of photosynthetic and respiratory metabolism are known from adapted eco­systems in arctic climates in summer. Adaptations, successions, and evolutions in an ecosystem can occur to permit high metabolism at low temperature. In the annual picture temperature does not begin to fall much until the cold fronts begin to pass through in November. The photosynthesis, however, begins to decline :gtarkedly (Fig. 7) as soon as the light income begins to decline in July. As established by many authors the temperatures in the shallow bays follow tha:t of the air masses that blow over them. There may be 15 degree centigrade range from one day to the next in winter. As illustrated in the case history presented for a February norther (Fig. 11) , rapidly falling temperatures have a profound effect on the gas ex­changes, but do not eliminate the metabolism. The hypothesis is proposed that the system and its organisms are sufficiently organized in their activity to keep the total metabolism in phase with food conditions as developed seasonally from light energy. In the annual cycle the total community metabolism is somewhat independent of temperature. What proportion of this community' regulatory activity may be controlled by the migratory behavior of populations and what proportion may take place within the physiological mechanisms of the single organisms is not known. The diurna! range of temperature like the diurna! range of oxygen content is a func­tion of the water depth with greater ranges in shallow water. In the water film communi­ties the daytime temperature approaches the upper limit (40ºC) for many organisms. THE ROLE OF TURBID BOTTOM MATERIALS The release of turbid materials is a dominant feature of the Texas area with organic Iaden silts and clays released in large quantity into the bays from the rivers, from dredging, from reagitation up from the bottom during storms, and from beach erosion. Turbid materials had two distinct effects on total metabolism as observed in this study. One effect of turbidity in reducing light penetration and thus reducing primary' produc­tion was discussed in the previous section on light. The other effect was a stimulation of the community respiration apparently dueto organic matter accompanying the inorganic turbidity. In the turbid water of Baffin Bay, in San Antonio Bay, during dredging in two places in Redfish Bay, in the floodwaters in Matagorda Bay, in the Louisiana hay at Hopedale receiving marsh detritus, and in the back bays receiving rivers, respiration was often in excess of photosynthesis suggesting that the import of organic matter was supporting consumption in addition to that produced by plants in situ. In Fig. 24 are data for the hypersaline Baffin Bay in which R exceeded P frequently, especially when salinities fell following rains. These days were like the waters of the Neuse River, North Carolina, in which respiration of a stream exceeded its photosynthesis with much of the consumption supported by organic matter running off the land (Hoskin, 1959). Similar conclusions were drawn by Pomeroy (1959), Ragotzkie (1959), and Tea! (1959) in their studies of the metabolism of the Sapelo lsland marsh waters. Although respiration was in excess of production in turbid water studies, the excess was not a Iarge one. In nature respiration was not in excess of photosynthesis by more than a factor of 2. Larger excesses of respiration over photosynthesis have been recorded in marine bays with known pollutions (Odum, 1960). A complicating aspect of the additions of turbid matter is the stimulus provided to photosynthesis indirectly' through the excess of respiration over photosynthesis. Where R is in excess of P, inorganic nutrients accumulate stimulating photosynthesis. Thus the turbid mixtures of organic and inorganic matter both interfere with photosynthesis by shielding light and stimulate it by indirectly raising inorganic nutrient levels. Studies by Wilson (1961) with the infra:red C02 analyzer method for assay of dis­solved and suspended organic matter have demonstrated the relatively high concentra­tions of organic matter found in the Texas bays with greatest concentrations up to 80 mg/ l in the turbid back bays so far studied including Baffin and Corpus Christi bays. Excess respiration over photosynthesis of 5 mg/ l / day (Fig. 24) would consmue a stor­ 80 10 o 60 o o 00 ,_ 40 >-­ z 30 ...J 20 <( V) 1o o 30 20 ,_ <( a N' ~ :E C) 10 BAFFIN BAY, TEXAS I I' I I I I I I / I I / I I I I I I , ~ ·~ , I II P', / '\ \ I / ' / /// .:-...-._-._..._.._-:{:'.>' JFMANJJASONOJFMANJJASONOJFMANJJASONOJFMAMJJASONO 1957 1958 1959 1960 Frc. '24. Metabolic data from Baffin Bay, Texas, during dry and wet periods. age of 80 ppm in about 16 days, but there is rarely decrease in respiration relative to photosynthesis. Apparently the inflow of extra-hay organic matter is keeping up with the consumption since the organic levels and excess respiration over photosynthesis are maintained particularly when the salinity is falling. THE ROLE OF AREA AND AGITATION Physical circulation is a normal requirement for many ecosystems supplying the nu­trients for photosynthesis and redistributing the organic matter and oxygen as fuel for consumers. In the Texas bays the areal extent determines the amount of circulation that can develop under the strong winds usual for the area. Armstrong Price (1947) and others have discussed the area of the bay's as a con­trolling factor on the depth of the bottom. They indicate that in small bays, insufficient wave energy develops to keep the bottoms from filling in with sediment to shallow levels. In deep bays mixing favorable to phQtosynthesis is partially offset by greater equilib­ Further Studi.es on Reaeratwn and Metabolism riurn depth rnaintained by scouring in the larger bays. The role of agitation on rnetah· olisrn is further rnasked by the rapid settling of the turbid materials during periods of relatively calm weather, when the additional penetration of light tends to offset any un­favorable aspect of diminished circulation. With the interplay of factors of area and agitation it is not easy to select natural experiments that delirnit the factors. A comparison may' be made between the metabolism in the small shallow sloughs (Table 1) as compared with the larger but equally shallow bays like the Laguna Madre (Table 1, Fig. 7). Similarly metabolism of enclosed and less agitated boat harbors may be compared with that of the open, well mixed bays (Table 1) of similar depth. In general the small littoral bodies of water, sloughs, and harbors, in spite of oppor­tunities for nutrient supplernent frorn littoral pollutions did not sustain greater produc· tion and rnetabolisrn than the larger wind-stirred, freely rnixing bays. THE RoLE OF NuTRIENTS lt is axiornatic that the rnaintenance of an adequate nutrient supply is essential to the rnaintenance of rnaxirnurn gross production. Maintenance of nutrients is accornplished in sorne systerns by the recyding of nutrients frorn the respiratory consurners. In sorne systerns nutrients are regularly irnported halancing those lost. Porneroy, working in the estuary of the Altarnaha river in Georgia (Porneroy, 1960) showed that where bays re­ceive flushing out of water with floods of low-nutrient, fresh water; accurnulated nu­trients tend to be flushed out. Such floods also kill off rnany of the larger organisrns so that their stored nutrients are also lost. Hoese (1960) docurnented a case of such flush· ing for Mesquite hay. In Texas hays studied it rnay be useful to propose three types of systems operating to supply adequate nutrients for high production rates: (a) hypersaline regirnes, (b) bot­torn grass-algal systems, (e) sy'sterns near inflows of high nutrient concentrations. (a) In the high salinity bays, the Laguna Madre and Ba.ffin hay, after long periods of sustained high salinity, nutrients have an opportunity to be accurnulated and recycled. As indicated in Table 2, high values of total phosphorus, 2 to 3 mg-atorn/ rn3, occur in TABLE 2 Total phosphorus in Texas bays. Groups of analyses are arrane:ed in order of decreasing salinity. Analyses by H. Bruce, R. W ard, and C. Oppenheimer Numher of s.amples mg-alom/ m3 HYPERSALINE BAYS, salinity, 50 to 70%0 Baffin Bay, July 26, 1957 8 2.7-5.2 Baffin Bay, August '15, 1957 9 3.4-4.2 Upper Laguna Madre, July 23, 1957 4 1.4--3.2 Upper La¡zuna Madre, August 1, 1957 8 3.4--4.2 GULF OF MEXICO, salinity, 33 to 36%<> Port Aransas jetties, July 15, 1957 8 2.0-2.2 Port Aransas jetties, July 23, '1957 l 1.8 Whistlin¡¡; buoy, Port Aransas, August 10, 1959 4 0.0--1.27 BOAT HARBORS, salinity, 28 to 34%0 Corpus Christi T head Harbor, August 10, 1959 2 1.6-1.9 Rockport Basin, August 5, 1957 8 2.0-4.0 GRASS FLATS, salinity, 29 to 33%<> Redfish hay, July 17, 1957 'l 1.3 Redfish hay, August 10, 1959 8 0.6'2-1.38 PLANKTONIC BAY, TURBIO, salinity, 10 to 28%<> Copano Bay, August 8, 1957 8 'l.6-2.4 Corpus Christi Bay, July 23, 1957 3 1.2-1.9 Corpus Christi Bay, August 10, 1959 6 0.80--0.97 dry years. The details of the daily uptake and regeneration have been shown by Bruce and Hood (1959). A similar high nutrient state has been established for inland waters in arid climates (Hutchinson, 1957). Bays that are stable with little flushing are the ones thought to develop higher pro· ductivity and nutrients self-regenerated. (b) In shallow water where bottom communities of grass and attached algae dominate the metabolism, flushing out of water due to floods or due to winter northers that drop the Gulf level are not so serious as in deeper bays, for much of the nutrient reservoir is not in the plankton but in the attached bottom materials. Providing the flushing does not kili the bottom system, the ecosystem can conserve nutrients for sustained high pro­duction. ( c) Where high nutrient levels in usable proportions are maintained in the inflowing water, flushing may not be detrimental to nutrient supplies. Nueces Bay and Oso Bay are examples of areas that often receive high nutrient contents due to municipal and industrial effiuents. lt is not always possible in field analyses to show when nutrients levels are limiting metabolism or when the reverse is actually the initial cause and effect (inadequate biota and metabolism for storage and circulation of nutrients). If the production is limited by sorne non-nutrient factor, the impoverished biota may be unable to store high con­centrations of nutrients in the geochemical recycling system. In any case, however, the nutrient level may be correlated with the gross production. In Table 2 the higher values of total phosphorus were associated with the areas of higher production in Baf­fin Bay and Laguna Madre whereas lower values, about one mg-atom/ m3, were found in Corpus Christi Bay. As the many' experiments on ponds indicate (Barrett, 1953; Hepher, 1959), adding concentrations of a nutrient like phosphorus may not have a sustained effect in many instances longer than the time for immediate uptake by the plants. The increase in photosynthesis in the fertilized slough (Table 1) followed by a decline in metabolism in subsequent weeks seemed to follow this pattern. Sustained increases in production require maintaining high rates of nutrient conservation and regeneration. Spot fertiliza­tion of the bays of Texas is likely to have the temporary effects found in fishpond work, but large sustained increases in fertility involve developing the nutrient conservation system like those already effective in sorne bays. Possible measures include development of hypersalinity' by diversion of runoffs, the development of more grass flats by control of turbidity and depth, and the channeling of nutrients of municipality and industry into areas to balance rate of flushout. The photosynthesis in the unfertilized natural grass beds around Port Mansfield (Table 1) was greater than the photosynthesis in the beds around the sewage outfall in Laguna grass flats near Ransom lsland. It is doubtful if one can stimulate metabolism much by fertilizing an ecosystem if it already has P equal to R and a fully developed standing crop in stable steady state, geochemically recycling nutrients at rates equal to the maximum photosynthetic demand possible at the available light intensity. For most of the Texas bays there is considerable opportunity to increase total pro­duction and consumption by changing the regime for nutrient supply. There is no reason why diversion of the flushing floods and sustained fertilization cannot maintain many bays much closer to the maximum productivities observed in the lower Laguna Madre Further Studies on Reaeration and Metabolism in 1960. Such an action program may be expected to double biological output of a half million acres. PoTENTIAL Yrnws The measurements of gross photosynthesis indicate the effectiveness of light in pro­ducing organic matter. In the natural aquatic communities of Texas P and R are often similar, and there is little net gain or loss of organic matter except for fish migrations and detritus export to the open Gulf. This balanced pattern may be changed by arti­ficial management. lf means similar to those of terrestrial agriculture can be employed to reduce respiration by weeding of consumers and if outside nutrients are added at a rate adequate to replace the normal supply' from respiratory regeneration, then a great part of the gross production might be channeled into organic storage for harvest. Since the rates of maximum gross photosynthesis measured in the Texas bays are equivalent to maximum rates of gross photosynthesis in agriculture, the potentials for eventful harvest and use are about the same. The grass flats because of their stability, nutrients conservation, and ease of manipu­lation can be the first of the large marine systems to be managed commercially either for increased fisheries and wildlife or for organized aquatic agriculture, harvesting plant matter. In arid areas along sea coasts the farming of the sea waters has the advantage over terrestrial agriculture in not being limited by water shortage. The hay waters of arid south Texas are suitable for providing world leadership in management of marine waters for useful purposes. Summary l. Further studies were made on the photosynthesis and respiratory metabolism of the marine bays of Texas with the diurnal oxygen method. On the basis of 123 new curves, the characteristics of metabolism of the planktonic and grassy bay's have been explored with emphasis on refinement of methods, natural experiments, and special situations. Measurements were included from 9 bays not heretofore studied metabolically· The bays included in this study are ali continuously well mixed by the winds without vertical stratifications. 2. Photosynthesis ·and respiration were generally similar and often in phase although the annual metabolism in single bays ranged from 0.5 gm/ m2/day minimum in winter to 40 gm/ m2/ day maximum in summer. 3. In the back bays receiving runoff, respiration often exceeded photosynthesis. Such conditions existed in low salinity bay·s and also in hypersaline bays after rains. 4. In bays where P and R were equal total metabolism was often greater than where P and R were not in balance and where one or the other part of the nutrient cycle between P and R may have been limiting. Metabolism and phosphorus levels were higher in hypersaline bays in which there was little flushing out by rivers. 5. The reaeration constant as computed from diurnal graphs were related to depth and wind velocity. The area-based reaeration constant K increased with water depth from about 0.1 gm/m2/hr at 10 cm depth to 5 gm/m2/hr/100% deficit in bays 4 m deep. The volume based reaeration constant k was fairly constant with depth, about 1.0 gm/l/ hr/100% deficit. Reaeration was surprisingly unimportant in the shallowest film communities measured. 6. The volume hased reaeration constant increases with wind velocity hy a factor of at least 2. 7. Severa! refinements in the diurna! graphic analyses were introduced to increase accuracy and avoid recurring artifacts. A photosynthetic hulge after sunset was found on many rate graphs of diurna} analysis and identified as an artifact due to seahreeze effects, easily recognizahle from data on wind velocities and a convex shape of the post­sunset oxygen graph. 8. lnferences were drawn from studies of particular case histories. Dredging produced a condition in which R exceeded P during dredging. After the shading of the turhidity disappeared, P was equal or higher than hefore. Respiration was also increased when strong winds stirred the bottom in a tropical storm. 9. The small shallow sloughs and pools isolated from the main bays contained tre­mendous ranges of diurna! temperature and oxygen content, but on an area basis only one receiving poUutants was as productive and metaholic as the best developed, larger, grassy hays. Film communities went anaerobic at night and developed blue-green algal mats. 10. Sorne of the graphs indicated a greater respiratory metabolism of oxygen just after dark than before dawn, suggesting diurna! rhythm of respiration related to the photosynthetic output. Efficiency of photosynthesis was slightly greater just after dawn than just hefore sunset suggesting the stimulatory effect of nighttime R on P. ll. Hexadecanol on two sloughs was temporary in effect and did not greatly affect the diffusion constant or metabolism. 12. A boat basin with active operations of small boa:ts retained apparent]y· near-normal photosynthetic and respiratory metabolism without going anaerobic at any time of night. 13. One sequence of diurna} data from the turbid, low salinity hayous in Louisiana marsh lands indicated a relatively low photosynthesis and respiration in April. 14. An enclosure with fiberglass walls placed overa turtle grass bed for experimental purposes did not immediately disrupt photosynthesis and respiratory metabolism. 15. In representative Texas bays the light of visible wave lengths suitable for photo­synthesis penetrating to the hottom averaged about 36% of surface intensity. Turbidities as indicated hy extinction coefficients per meter for a visible range photometer without filters ranged from 7.7 per m in turhid hack bays to 0.33 in the lower Laguna Madre at Brownsville and O.U on the Gulf shelf off Port Aransas. In most bays the critical depth for phytoplankton growth was not often exceeded. 16. A close hour by hour correlation of photosynthesis with light intensity was ob­served in the daily measurements during passage of fronts, or in comparisons of suc­cessive clear and cloudy days. Turbid bays contained much less photosynthesis than sorne clear bays at similar light intensity. lí. The graph of photosynthesis versus light intensity was without a light saturation point. High efficiency was found at low light intensity, but maximum gross production was found at maximum light intensity. 18. Maximum efficiencies, productivities, and sustained respiration were found in natural, high salinity, grass flat systems with values equal to those in artificial sewage ponds. Values were as great as in tropical reefs with photosynthetic efficiencies as high as other aquatic communities of maximum fertility on earth. 19. To produce maximum total photosynthesis in ali of the waters of Texas, measures for management should include: reducing turbidity, eliminating irregular flushing of flood waters, developing grass bottoms, retaining wind driven circulation, and adjust­ing water depths of shallow and deep areas towards an average depth of 0.5 m. Acknowledgments These studies during 1958-60 were made possible by the assistance of members of the diurnal analysis teams which included Chester Runnels, John Meadows, Maryanne Chilen, Gertrude Kone, John Shanklin, Steve Bailey, Frank Schlicht, Richard Davis, and Niki Roberts. The four year Laguna series included aid of Charles Hoskin, K. Park, E. Simmons, H. Bruce, T. Hellier, G. Garza, C. Wise, E. Guerra, N. Armstrong, J. Pirson and others. Many of the studies were made with the cooperation and aid of The Texas Game and Fish Commission through courtesy of Howard Lee, Ernest Sirnmons, Joe Breuer, Ron Schultz and their boat crews. Data on the sewage ponds were made available by Dr. David Smallhorst from an un­published report by V. M. Ehlers, T. W. Ray, and E. C. Nelson entitled, "Production of oxygen by photosy'nthesis induced by artificial light on algae in sewage ponds." This manuscript prepared in 1949 carries the following acknowledgment: "Made possible through the cooperation of the Air Force of the Training Command, by Authority of General A. C. Kincaid, Chief of Staff, Dr. George W. Cox, State Health Officer, and the Texas Water and Sanitation Research Foundation. Dr. J. K. G. Silvey identified the forms of algae. Mr. W. C. Churchwell constructed and supervised operation of the pilot plant." Data from Hopedale, Louisiana, were obtained through courtesy of Dr. K. M. Rae and Dr. George Rounsefell supervising the Mississippi dredging survey of the U. S. Fish and Wildlife Service in contract with Texas A & M Research Foundation. These curves were obtained with assistance of Lamarr Trott, Dean Letzring, C. Mock, and other personnel of the A &M field staff at Hopedale. Hexadecanol was provided by Dr. E. P. Whitlow of the Southwest Research lnstitute. We are grateful to Dr. Stuart Grossman and Mrs. L. D. McCall for aid in drafting figures. Literature Cited Barrett, P. H. 1953. Relationship between alkalinity and absorption and regeneration of added phosphorus in fertilized trout lakes. Trans. Amer. Fish. Soc. 82: 78-90. Beyers, R. J. 1962. Tbe metabolism of twelve aquatic laboratory micro-ecosystems. Ph.D. Disserta· tion, The University of Texas. 195 p. Bruce, H . E., and D. W. Hood. 1959. Diurna! inorganic phosphate variations in Texas bays. Publ. lnst. Mar. Sci. Univ. Tex. 6: 133-145. Ehlers, V. M., T. W. Ray, and E. C. Nelson. 1949. Production of oxygen by photosynthesis induced by artificial light on algae in sewage lagoons. Unpublished report, Texas State Department of Health. Fisk, H. H. 1959. Padre Island and Laguna Madre flats of coastal South Texas, p. 103-152. In 2nd Coastal Geography Conference of Coastal Studies lnstitute, Louisiana State University. Gameson, A. L. H., and M. J. Barrett. 1958. Oxidation, reaeration, and mixing in the Thames Estuary, p. 63-91. In Oxygen relationships in streams. Technical Report of Robert A. Taft Sanitary Engineering Center, W58..:2. Gessner, F., and F. Pannier. 1958. Der Sauerstoffverbrauch der Wasserpflanzen bei verschiedenen 'Sauerstoffspannungen. Hydrobiologia 10 : 323-351. Harris, W. P., and W. W. Meinke. 1959. Evaporation loss reduction. Paper presented to Texas A&M College Conference on Water. Mimeographed. Hellier, T. R. 1962. Fish production studies in relation to photosynthesis in the Laguna Madre of Texas. Publ. lnst. Mar. Sci. Univ. Tex. 8: 1-22. Hellier, T. R., and L. S. Kornicker. 1962. Effect of hydraulic dredging on sedimentation. Pub!. lnst. Mar. Sci. Univ. Tex. 8: 212-215. Hepher, B. 1959. Chemical fluctuations of waters of fertilized and unfertilized fishponds in a sub­tropical clima te. Bamidgeh 2: 2-22. Hoese, H. D. 1960. Biotic changes in a hay associated with the end of a drought. Limnol. Oceanogr. 5: 326-336. Hood, D. W. 1953. A hydrographic and chemical survey of Corpus Christi Bay and connecting water bodies. Texas A&M Research Foundation Report No. 40, p. 1-23. Hoskin, C. M. 1959. Studies of oxygen metabolism of streams of North Carolina. Pub!. lnst. Mar. Sci. Univ. Tex. 6: 186--192. Hutchinson, G. E. 1957. A treatise on limnology. Vol. 1, Geography, physics, and chemistry. John Wiley, N. Y. "1015 p. Murphy, G. l. 1962. Effect of mixing depth and turbidity on the productivity of fresh-water im­poundments. Trans. Amer. Fish. Soc. 91: 69-76. O'Connor, D. J. 1958. The measurement and calculation of stream reaeration ratio, p. ·3,~. In Oxygen relationships in streams. Technical Report of Robert A. Taft Sanitary Engineering Center, W58-2. Odum, H. T. 1956. Primary production in flowing waters. Limnol. Oceanog. 1(2): w2-..:111. ----. 1957. Trophic structure and productivity of Silver Springs, Florida. Eco!. Monogr. 27: 55-:112. ----. 1960. Analysis of diurna! oxygen curves for the assay of reaeration rates and metabol­ism in polluted marine bays, p. 547-555. In Pearson, E. A., Proceeding of the First lnternational Conference on Waste Disposal in the Marine Environment. Odum, H. T., P. R. Burkholder, and J. Rivero. 1959. Measurements of productivity of turtle grass flats, reefs, and the Bahía Fosforescente of southern Puerto Rico. Pub!. lnst. Mar. Sci. Univ. Tex. 6: 159_.:170. Odum, H. T., and C. M. Hoskin. 1958. Comparative studies of the metabolism of marine waters. Publ. lnst. Mar. Sci. Univ. Tex. 5: 16--46. Odum, H. T., W. M. McConnell, and W. Abbott. 1958. The chlorophyll A of communities. Pub!. lnst. Mar. Sci. Univ. Tex. 5: 65-97. Odum, H. T., and E. P. Odum. 1959. Principies and concepts pertaining to energy in ecological systems, Chapter 3. In Odum, E. P., Fundamentals of ecology, Saunders, Philadelphia. 521 p. Park, K., D. W. Hood, and H. T. Odum. 1958. Diurna! pH variation in Texas bays, and its applica­ tion to primary production estimation. Pub!. Inst. Mar. Sci. Univ. Tex. 5: 47-64. Phelps, E. B. 1944. Stream sanitation. John Wiley and Sons, N. Y. Pomeroy, L. R. 1959. Alga! productivity in the salt marshes of Georgia. Limnol. Oceanogr. 4(4): 386--397. ----. 1960. The phosphorus cycle in estuaries. Paper presented at Amer. Soc. of Limnol. and Oceanogr. meeting at Stillwater, Oklahoma, (August, 1960). Price, W. A. 1947. Equilibrium of fonn and forces in tidal basins of coast of Texas and Louisiana. Bull. Amer. Asso. Petrol. Geol. 31: 1619-1663. Ragotzkie, R. A. 1959. Plankton productivity in estuarine waters of Georgia. Pub!. lnst. Mar. Sci. Univ. Tex. 6: 146--158. Ryther, J. A. 1959. The potential productivity of the sea. Science 130(3376): 602-608. Stalfelt, M. G. 1960. Temperatur, p. 10~116. In Pirson, A., Handbuch der Pflanzen Physiologie, bd. 5, Die C02 assimilation, Teil 1, Springer, Stuttgart. 868 p. Sverdrup, H. U. '1953. On conditions for the vernal blooming of phytoplankton. J. du Conseil 18: '287...:295. Tea!, J. M. 1959. Energy flow in the salt marsh ecosystem. 1958 Salt marsh conference, Sapelo lsland, Mar. lnst. University of Georgia, p. 101-103. Velz, C. J. 1939. Deoxygenation and reoxygenation. Trans. Amer. Soc. Civ. Engnr. 105: 560-572. Verduin, J. 1957. Daytime variations in phytoplankton photosynthesis. Limnol. Oceanogr. 2: 333-336. Wilson, R. 1961. Measurement of organic carbon in sea water. Limnol. Oceanogr. 6: 259-261. Sorne Bacteria! Populations in Turbid and Clear Sea Water Near Port Aransas, Texas C. H. ÜPPENHEIMER1 AND HoLGER W. JANNASCH2 lnstitute of Marine Science Port Aransas, Texas Abstract Direct counts were made of bacteria in clear and turbid sea waters near Port Aransas, Texas including waters of the Gulf beach, the Laguna Madre, and the Redfish Bay turtle grass areas. Counts ranged from 900,000 per mi outside the Gulf surf to 28,800,000 in turbid water along the shore of Redfish Bay. Counts were used to estímate bacteria] biomass (0.2 to 6 g/m3 ) and potential oxygen demand. Introduction The extensive, shallow, marine hay system of the Central Texas coast and the Gulf beach waters are noted for turbidity caused by the presence of clays, detritus, and living organisms. Visibility in the hay' water is often limited to a few centimeters. Occasionally, for an unknown reason, portions of the bays become clear. At other times, e.g., after a storm, the water appears to be nearly a colloidal sol because of the high content of par­ticulate material in suspension_ The suspended material slowly settles out during quiescent periods and becomes resuspended by wave action during wind storms_ As a result, the gradual sloping beaches and areas with vegetation exposed at the water's edge have sediments of finer particles. In May, 1958, experiments were conducted to determine the bacteria} populations in turbid and clear water within the Central Texas hay system and in the surf zone of the Gulf of Mexico. Bacteria! populations were measured by direct microscopic method. Areas Sampled Fig. 1 illustrates the general locality of investigation. Surf samples were taken from an area near Padre lsland Park where the water was clear. Samples were collected from the active surf zone at the breaking point of the waves and just outside the surf zone in deeper water. A second series of samples was collected from the Laguna Madre area near Pita lsland on the west edge of the hay taken at approximately: mid-depth (30 cm) near shoreline in turbid water over a bed of Diplanthera; mid-depth (30 cm) over a sandy beach in clear water; mid-depth (30 cm) in an area where bottom sediment was stirred up by wading during our collecting activities; and mid-depth (30 cm) in clear water at a sandy point. A third series of samples was taken along the west edge of Redfish Bay in a small cove: one sample was taken in very turbid water at mid-depth in an area where considerable amounts of decaying sea grass had been deposited on the bottom; one sample was taken in turbid water above a Diplanthera bed; one in clear 1 Present address, University of Miami Marine Laboratory, Virginia Key, Florida. 2 Present address, Department of Microbiology, University of Gottingen, Gottingen, Germany. Sorne Bacteri.al Populmions in Turbiá and Clear Sea Water F1c. l. Sample areas at Redfish Bay, Pita lsland, and the beach of the Gulf of Mexico. water over an attached Thalassia bed; and one near a sewage disposal outlet for part of the city of Aransas Pass. The wind activity for the week prior to sampling was relatively quiet and the larger particulate materials had settled out. The average tide was estimated at about 10 cm. The turbid waters had small particulate materials which had not settled out or were colloidal in nature. The clear areas were typical of portions of the bays with large amounts of benthic plants and water less than 60 cm in depth. At present the authors have found no literature describing the colloidal aspects of turbid water in these shallow marine bays. Collier and Hedgpeth (1950) described sorne hydrographic conditions, and Shepard and Moore ( 1955) have reported hydrographical and geological details of the a rea. Procedure for Direct Microscopic Counts Bay water was collected in 500 mi sterile bottles and immediately fixed with formalin at a final concentration of two per cent. Formalin treated samples were analyzed at the lnstitute of Marine Science at Port Aransas. Direct counts were determined by· a modi­fied Cholodny technique presented by Jannasch and Jones (1959). Duplicate aliquots of 50 to 200 ml samples ( depending on the turbidity) were concentrated to less than 5 mi but not to dryness with a millipore filter apparatus. The millipore filter retained particles of 0.4 microns and larger. The concentrate was placed in a small glass vial and filled with filtered distilled water to 5 mi volume. Duplicate aliquots of 0.01 mi of the con­centrate were pipetted onto clean glass slides. The round drop, formed on the slide, Some Bacteria[ Populations in Turbid and Clear Sea Water was dried in air and stained for 12 hours with a filtered mixture of two per cent aqueous erythrosin and five per cent phenol. The slides were washed with distilled water and dried at room temperature. Direct bacteria counts were made with a Reichert Anoptral phase microscope to aid in the recognition of bacteria. Sufficient fields were counted to provide a calculated statisti­cal variance of less than five per cent. Different morphological types of bacteria were tabulated during the counting procedure. Total numbers of bacteria were calculated from values for the area of each sample spot on the slides and the area of the microscopic field (average number of bacteria per microscopic field multiplied by the concentration factor). Biomass was calculated using the mass 2 X l0-13 g for one bacterium as taken from Kriss ( l 959b) . Results and Discussion The bacteria! numbers found in the samples are reported in Table l. Bacteria must constitute a considerable fraction of the total particulate load in the waters of the bays. Unfortunately the total particulate load in the water was not measured at the time of the experiments. However a particulate load of 39.9 g/m3 ( dry wt) has been recently found in water near the lnstitute of Marine Science. The amount of dry bacteria] mass (cor­rected for water content by assuming the bacteria to be 80 per cent water) in Redfish Bay sample 1 is 1.16 g/ m3• If the values for biomass and particulate load are compared, the bacteria represent approximately 3 per cent of the total load. In addition we can calculate approximate]y· the total organic carbon supplied by the bacteria. Wilson (1961) gives an average organic carbon value of 4 g/m3 for Redfish Bay water. Assum­ing that the bacteria are 5 per cent organic carbon, the 5.8 g/m3 biomass found in sample 1 contains 0.29 g organic carbon/m3• If the bacteria] carbon is compared with Wilson's value, we find that 7.2 per cent of the total carbon is derived from bacteria. It is realized that these are rather gross assumptions but the values do give sorne concept of the importance of the bacteria under sorne conditions. No significantly large differences were noted between bacteria] numbers in clear and turbid water and the one Gulf sample. The Gulf sample outside the surf zone had the TABLE 1 Average numbers o! bacteria per mi and biomass by direct microscopic counts of water from shallow marine bays in May, 1958 from duplicate samples \l'ater depth Average number of Biomass A rea in cm bacteria per mi g/mS SURF GULF BEACH NEAR PADRE ISLAND PARK 1 Surf zone 120 1,600,000 0.32 2 Outside surf zone clear water 180 900,000 0.18 PITA ISLAND, LAGUNA MADRE 1 Near shore above Diplanthera bed, turbid water 91 9,000,000 1.8 2 Above sandy beach, clear water 60 20,000,000 4.0 3 In clear water 60 4,500,000 0.9 4 In the same clear water after sediment was stirred up by wading 60 52,000,000 10.4 REDFISH BAY 1 Near edge in tur'bid water 60 28,800,000 5.8 2 Muddy water over Diplanthera beds 60 2'2,200,000 4.4 3 Clear water over Thalassia beds 60 2,700,000 0.54 4 Near sewage outfall, Aransas Pass 60 25,800,000 5.10 Some Bacterial Populations in Turbül and Clear Sea Water lowest bacteria} population. The total biomass of bacteria is high for natural unpolluted marine waters as compared to the data of Kriss (1959a and 1959b) in the Pacific and Black Sea, and the data of Jannasch and Jones (1959). The bacterial biomass of our shallow bays is approximately 10 times the largest value given by Kriss for the Black Sea. The values in Table 1 do compare with those of Jannasch (1958) for Naples Har­bor and ZoBell and Feltham (1942) for Mission Bay, California. lt is interesting that coccoid forms apparently predominated in the hay waters at the time of collection (Table 2). Direct microscopic examinations of the sedimeni:s of the bays by the senior TABLE 2 Percentage of types of bacteria Per cent of tolal Area Rods Sp irilla Vibrio Cocci 0.9 0.7 1.3 97.1 2 0.2 0.3 99.5 3 1.7 0.2 1.3 95.5 4 '2.9 0.3 1.3 9S.5 5 LO 0.1 0.2 98.7 6 0.9 0.2 2.3 96.6 7 1.9 0.2 0.8 97.1 8 1.6 0.6 1.9 95.9 9 4.8 1.3 1.0 92.9 10 3.4 '2.5 3.2 90.9 author indicate that the rod shaped organisms predominate there. During the stronger winds, from 20 to 60 mph, the surface sediment layers are mixed into the water by wave action. In clear water at Pita Island (Sample 3) the bacterial count was 4.5 X 106 per ml. When the surface sediments were mechanically mixed into the water, the count increased to 5.2 X 107 • The large indigenous populations may reflect large amounts of nutrients and a rapid potential metabolic activity. If one uses the general value of ZoBell (1946) for indi­vidual bacterial oxygen consumption (20.9 X 10-12 mg oxygen per cell per hr at 22ºC) the calculated oxygen uptake at station 5 is 26 mg oxygen/l/day, assuming all bacteria to be active. One must realize, however, that although bacteria may be present, they are active only in the presence of food and favorable conditions. Living organisms which die may be immediately attacked by bacteria, and those bacteria which may have been in a resting state previously, immediately become active decomposers. Such a situation has been recorded by Oppenheimer (1960) where bacteria attach to dead but not living sedimentary diatoms. The large bacteria} populations and the high organic content of the bays (1 to 80 mg/ l, Wilson, 1961) suggest the possibility of a large oxygen demand which may exceed the usual supply from atmospheric diffusion. If the bacteria were active and oxygen only available from photosynthesis and diffusion, one would expect the bays to become anaerobic at times. The senior author has not found anaerobic water conditions in unpolluted bays during three years of field investigarions. The continua} wind action over the shallow waters stirs the water, thus mixing oxygen from the surface. Mixing is a common occurrence, and salinity and temperature profiles are normally uniform except during tidal fluctuations near the pass entrances, after heavy rainfall, and during abrupt air temperature changes due to northers (Oppenheimer, Travis and Woodfin, Some B78.0 >85 99• 99• Color of zone Dark Dusky Lustrous Yellowish Pale brown blue-grn blue-grn blue-grn yellow pink at pink at bottom top • 1% Argon. Two types of experiments were performed. Gravimetric experiments were conducted using whole pieces of mat community including both plants and animals. These pieces were grown in cultures and their dry weight changes observed. Morphometric experi­ments were performed using isolated filaments of Lyngbya con/ ervoides. These fila­ments were grown in impure drop cultures and their length changes observed. In addition, especially for Lyngbya the laboratory cultures were compared quali­ Algal Mat Communities of Lyngbya co~fervoides (C. Agardh) Gomont tatively with lagoon mat samples. They were compared as to thickness and transparency of the sheath, predominating color of photosynthetic pigments, shape and graininess of the protoplast. Six-liter glass dessicator jars were used as chambers in which the conditions of growth within the mat samples were simulated. A water bath was substituted for the dessicant to provide a water saturated atmosphere. The samples were placed into 1 cm deep clean plastic boxes on the ceramic shell of the dessicator and covered with nat­ural pond water. Salt content of the pond water was 2.6 per cent. The chamber used for growing cultures under aerobic conditions was fitted with a blotter-paper gasket between the lid and the jar. This gasket provided an exchange of air with the outside atmosphere but kept evaporation to a mínimum. The blotter ex­tending beyond the chamber reduced the sunlight falling on the cultures. By varying the width of the blotter, the amount of light reaching the cultures could be changed without altering the spectral composition. The chambers for anaerobic studies were fitted with sealed lids. Oxygen-free nitrogen was used to replace air in the chambers. The gas in the chambers were tested before and after each experiment for the presence of oxygen using a Beckman GCI gas chromato· graph. The cultures grown anaerobically were incubated in total darkness. Duration of experiment, temperatures, illumination, and other conditions under which the cultures were grown are shown in Table 2. The mat samples, used in the incubation chambers, were washed with tap water to remove soil, organic detritis, and larger metazoa. Examination of the washed and un­washed samples indicated that larger algae were retained intact when washed but sorne of the smaller living organisms were removed. The samples were then dried at 40ºC for 24 hours. The gain or loss due to growth of the community was measured on this dry weight basis. Heat drying of the living mat at 40ºC may have had little effect on the viability of most of the microorganisms, because organisms in natural mat communities are normally exposed to large changes in temperature and water content. When drfod mat material was placed in pond water, alga! filaments and bacteria began to show motility within one hour. Weight changes after the first two hours of imbibing water were negligible. Approximately 0.2 to 1.5 g dry weight samples were used for the ex­perimental cultures. Aliquot amounts of the natural pond water, containing organic compounds, were dried and the residue weighed. The dry weight of the pond water residue per volume used in the culture boxes was then subtracted from the final weight of the incubated samples. Protoplasmic weight increase by alga! mat samples in excess of the pond water residue weight was interpreted as growth with carbon (C02 ) derived from the water and the chamber's atmosphere. The growth increases in Lyngbya confervoides, the alga which comprised over 80 per cent of the living community in the mat (optical estímate), were obtained by morphom· etry. Single filaments of this blue-green alga were isolated with microdissecting needles, washed in severa! exchanges of distilled water and placed on clean microslides. A drop of fi!tered marine pond water (16%0 salinity) was added to the slide. A cover slip was carefully dropped over the water drop. A thin film of petroleum jelly was applied on the slide around the edge of the cover slip without sealing it to prevent Ioss of the filaments. Usually four to six filaments per slide were used. At the beginning and end of each experiment the microslides containing the individual filaments were placed on the stage of a compound microscope and the filaments were projected by means of a mirror and strong light source and measured directly on a draw· ing board. It was usually possible to recognize individual filaments due to the presence of certain damaged cells, sheaths, artifacts, or other identifiable structures. The projected images of the trichomes within the sheaths were measured with a precision millimeter rule. Calibration of the images projected on the board was accomplished by establishing for each magnification used (400X and lOOOX) the number of microns of microscopic field (obtained with a stage micrometer) per millimeter on the drawing board. A meas­uring error of plus or minus 0.005 mm was obtained by this method. The slides containing algal filaments were floated on foam plastic in 5 mm deep water baths of distilled water in si de small rectangular clear plastic boxes ( 6 cm X 12 cm X 2 cm) with tight fitting lids. Holes, bored one in each end of the lid and stop­pered with corks were provided to flush out normal air and to replace it with nitrogen for anaerobic growth experiments. A small shell vial was placed inside the pill box and filled with boiled alkaline methylene blue indicator solution to show the presence of oxygen in anaerobic growth experiments. The lid of the box was sealed with a plastic clay substance used by electricians in place of insulation tape. Pill boxes used for aerobic growth studies were similar in design but the lids were not sealed. Cultures for morphometric studies were incubated only three days. The buoy'ancy of hormogones was determined by placing a number o·f hormogones of four to ten cells each in three depression slide chambers. One depression slide was filled with fresh water and the others with salt water (3% and 20% ). A cover slip was firmly sealed over the depression with petroleum jelly. The slides were turned end to end a few times to agitate the hormogones and placed vertically on the stage of a horizontally tilted compound microscope. This arrangement permitted gravity to settle negatively buoyant hormogones in the bottom of the depression slide while positively buoyant spores floated to the top. Counts were made of the number of hormogones which sank or flo.ated. Empty sheaths and living filaments of Lyngbya were observed, using the same method. Measuremerits of light penetration through layers of algal mat were made with a photometer with a selenium cell. Results DESCRIPTION OF ALGAL F1LAMENTS FROM THE ZoNEs IN THE MAT In Fig. 2-6 are presented microphotographs of alga! filaments from the mat and those cultures in similar light regimes. Near the surface in zone A (Fig. 2) the alga! sheaths are blackened giving the whole mata darkened coloration. In zone B there is a transition with loss of sheath coloration ( Fig. 3) . Below in zone C, the sheaths are clear. Many hormogones were being formed. The protoplasts were fine grained. The filaments were lustrous blue-green with a brilliant color not seen above or below this zone ( Fig. 4). Under zone C, in zone D, 3 to 8 mm below the surface is a yellowish carotene-tinted layer with many dead sheaths, walls, remains of worms and crustaceans, increasing num­bers of colorless flagellates and bacteria and sorne purple bacteria. The living filaments F1c. '2. Zone A. Photomicrographs of filaments of Lyngbya confervoides extracted from the surface crust of a mud flat alga] mat designated as Zone A. Note the sheath coloration. F1G. 3. Zone B. Photomicrographs of filaments of Lyngbya confervoides teased from the immediate subsurface !ayer, designated as Zone B. Note the thick sheaths, reduced opacity of the sheaths, and larger number of intact, unplasmolized cells. FrG. 4. Zone C. Photomicrographs of Lyngbya confávoides obtained from a mud flat alga! mat. The alga was removed from Zone C. Note the clear sheath walls, healthy looking cells, and presence of honnogones. Alga}, Mat Communities of Lyngbya confervoides (C. Agardh) Gomont of Lyngbya possessed thin colorless sheaths and lusterless yellowish cells with many vacuoles. The protoplasts were coarsely grained. Many hormogones were being produced. Amid the organic debris in zone D was a rich bacterial flora. ( Fig. 5) . The lower-most zone E (4 to 10 mm below the surface) of the living alga! mat com­ munity rests on or in a black, organic, silty, sandy sediment. The mat tends to merge directly with the physical and biological complex of these surface sediments when wet or covered with water. If the mat is exposed to air it dries and shrinks pulling away from the sediment. No light could be detected (Table 1) more than a millimeter into the band. The layer is reddish yellow due to the presence of both Lyngbya conf ervoúles and an autotrophic purple bacterium. There are also many colorless flageHates and bacteria including Beggiota sp., diatoms, and blue-green algae of the genus Oscillatoria, Phor­ midium, and Schizothrix (Fig. 6) . The zone has an odor of hydrogen sulfide. GROWTH OF F1LAMENTS UNDER CoNDITIONs S1MuLATING THE NATURAL ZoNES In Table 3 and Table 4 are summarized the results of the growth studies according to the zone. In each table is given the mean, standard deviation and the number of measurements of length of the trichomes. Positive increase in weight (Table 3) was observed only in experiments simulating zones C and D, the same zones with the green appearance and thin sheaths. Apparently neither the surface conditions with the high light intensities nor the deep anaerobic conditions with little or no light were able to support net growth or the community dominant. Positive increases in length o.f trichomes were also found in conditions of leve! C and D. In addition a few instances of increased length without increase in weight were found in conditions of zone E. Whether these cases involved heterotrophic nutrition, elongation without gravimetric gain, is not certain. Of much interest is the positive growths in length and weight · of filaments in con­ditions simulating zone D in the dark. lt is possible that heterotrophic growth was taking place. It is possible that changes in salinity during transfer may have caused water up· take also. Thus growth was observed in conditions simulating the lower intensities of the lighted zones and the layerimmediately below the lighted zone. Discussion of the Role of Each L~yer Each zone (A thr9~gh E) in the alga! mat profile appears to represent a habitat whfr:h differs with respect to trophic leve! from adjacent zones: Furthermore, additive growth appears to occur mostly in the central portion of the mat from zones B through the upper part of E. ZoNE A The role of the darkly stained surface !ayer in the community may be primarily that of a light and temperature shield for the sublayers of living organisms. Filaments under intense sunlight severa! millimeters deep within the mat crust are deeply staincd. There­fore, as summer approaches the density of the pigment in the crust of the mat increases iO Alga}, Mat Communities o/ Lyngbya confervoides (C. Agardh) Gomont F1c. 5. Zone D. Photomicrographs of Lyngbya confervoides taken from Zone D, a yellow-tinted zone below the more lustrous blue-green band. Note the thin sheath walls, the presence of hormogones, and healthy appearance of the cells. F1c. 6. Zone E. Photomicrographs of Lyngbya confervoides in Zone E near and at the bottom of the algal mat. Note the thin sheath walls, contraction of the protoplasts, balling-up of the cytoplasm, and presence of vacuoles. Algal, Mat Communities o/ Lyngbya confervoides (C. Agardh) Gomont TABLE 3 Gravimetric data for alga! mat cultures of Lyngbya confervoides grown under conditions simulating the zones found in the natural alga! mat (See Table 1) Simulated ZOhf' Beginning dry wt Mean SD N Mean Final dry w t SD N Growlh rale in g/week* Mean SD N A '1.34-05 0.3962 12 1.2749 0.3819 12 --0.051 0.031 1'2 B 0.1781 0.0921 5 0.1658 0.0797 5 --0.047 0.111 5 e 0.8161 0.9383 8 0.9491 0.8589 8 0.72 0.70 8 D 0.0672 0.0172 12 0.1032 0.0122 1'2 0.62 0.43 12 E 0.107 0.025 16 0.083 0.014 16 -0.206 0.126 16 • Growth rate is ha.sed on a sample with an initial dry weight of 1 g. 4 sq cm of algal mal equals approximately l g. dry weight. SD Standard Deviation. N Number of measuremenls. TABLE 4 Morphometric data for alga! mat cultures of Lyngbra confervoidcs grown on microslides under conditions simulating those found in the natural alga! mat (See Table 1) Simula!ed zonal lnitial lengtb trichomes in mm Final lcngth tri<"homes Per cent change in length condilions Mean SD N Mean SD N Mean SD N A 0.80 0.32 17 0.71 0.29 17 -ll.O 6.3 17 B 0.82 0.24 8 0.81 0.~2 8 -0.4 12.4 8 e 0.95 0.21 8 0.99 0.'24 8 3.5 10.7 8 D 0.252 0.302 9 0.363 0.568 9 24.8 26.3 9 E 0.89 0.29 18 0.86 0.30 18 -2.9 9.7 18 SD Standard Deviation. N Number of measuremenls. and becomes more and more effective as a light shield. This conclusion was reached by the writers when they observed that nearly 95 per cent of the incident light (Table 1) is lost within the first 0.5 to 1.0 mm of the average alga! mat crust. The crust may suffer a general net loss, as suggested by the data in experiments on zone A (Table 3 and 4). In Fig. 7 a growth rate curve for the entire mat profile has been constructed upon data from the gravimetric experiments. In zone A of this postu­lated growth curve, the compensation point has been estimated to occur actually below the surface crust of the mat. lf there is a net loss in the surface !ayer, how is it possible for the crust to maintain itself? Patches of surface crust are often removed by high winds exposing the subsurface layers. Alternate drying and wetting of the mat tends to cause shrinkage and sloughing off of sections which may be floated or blown away. Yet, the surface !ayer appcars to be renewed continually. Newly exposed mat surfaces will assume crustal characteristics. Lyngbya has motility which was often observed by the writers. The alga was also ob­served to have positive phototropism in moderate light (see Burkholder, 1934). Migra· tion to the surface after dark and on overcast days would be possible. Hormogones like­wise may help repopulate the surface by means of flotation. Results of an experiment (Table 5) indicated that in water containing 3 per cent salt or more the buoyancy of hormogones was positive. Pieces of mat or whole sections were observed floating on the surface of the water sorne seasons. ZoNE B Sorne additive growth is probably contributed to the mat community frcm zone B beneath the light and heat shield of the surface crust. Data from experiments simulating zone B (Tables 3 and 4) support this conclusion and the growth curve shown in Fig. 7 indicates the probable trophic relationship of this subsurface )ayer. GRO'<>sition o/ Organic Carbon in Surface Sediments ductive shallow marine bays of the Texas coast were measured by an indirect method involving the study of the changes in total organic matter. Seasonal variations, lateral variation, vertical variation, and effect of the types of sediments can be estimated. One must assume, however, that the changes in the content of organic matter are directly re­lated to the activities of microorganisms. Where large burrowing organisms are not abundant, it may be assumed that the net organic matter in the sediment will not be changed much by the activities of the larger invertebrates. The following data are de­rived from approximately 8 months of research in 1958 and 1959 on the changes of or­ganic matter and microorganisms in Red Fish Bay, Texas (Fig. 1.). o M KlOO FrG. 'l. Approximate locations of five field stations in Redfish Bay. History The total amount of organic matter in marine sediments has, in the past, been deter­mined by four methods, each procedure having inherent errors (a recent survey· of carbon procedures is given by Duursma, 1961): l. I gnition o/ sample and determination of loss in weight. The ignition method is not selective for organic matter because calcium carbonate and other volatile inorganic ma­terials may' be included. Trask (1939) has shown that fine clays lose more water than sandy material, causing error in ignition studies. 2. Determination o/ a reduction number. The method of Schollenberger ( 1927) for the determination of the reduction of chromic acid by sediment has been modified by Trask (1939). The amount of reduction has been considered an index of total organic content. However, the type and state of oxidation-reduction of the organic material in the sediments will affect the amount of chromic acid which can be reduced. 3. Extraction o/ organic matter. The amount of time needed for extraction limits its usefulness. Also, most solvents are not capable of removing ali the organic matter. 4. Determination o/ organic carbon by wet combustion. The determination of organic carbon and the use of ·a conversion factor of 2 to convert carbon to organic mat­ter was first suggested by Boysen-Jensen (1914). Waksman (1933) suggested a fac­tor of 1.887, and Trask (1932) proposed using a factor of 1.7 for marine sediments. In comparing the total organic matter with the organic carbon values of the same sediment Microbial Decomposition o/ Organic Carbon in Sur/ace Sediments samples, Bader (1954) found that conversion factors varied from 1.49 to 2.5. Therefore, Bader suggested that organic carbon values per se be reported. Much of the information on the distribution of organic matter in ancient and recent marine and estuarine bottom deposits has been published by Trask (1932, 1939), who reported that the amount of organic carbon in sediment may be inversely related to par­ticle size. Krumbein and Caldwell (1939), Emery and Rittenberg ( 1952) , and Bader (1954) have also observed in recent and older sediments that the organic carbon in­creases with decreasing grain size. In their studies of Central Texas Gulf coast sedi­mentation, Shepard and Moore (1955) found no direct correlation between percentage of carbon and percentage of clay. Organic carbon is normally found to decrease with an increase in sample depth from mud surface (Trask, 1932, 1939; Krumbein and Caldwell, 1939). Shepard and Moore (1955) and Murray (1956), however, find no marked variation in carbon with depth of sediments, and often a slight increase in organic carbon with increased depth is ob­served. The effects of sample depth and type of sediment on bacteria} population in sediments have been studied by Emery and Rittenberg (1952). They indicate that the upper layers of sediments usually contain larger bacteria! populations. However, occasionally subsur· face samples give higher counts than surface samples. A larger bacteria! population in a subsurface sample appears to be correlated with an abrupt increase in water content and decrease in cohesiveness. Reuszer (1933) stated that the distribution of bacteria is re­lated directly to the organic content of the sedimentary layers. The higher organic con­tent of clays and silts is perhaps responsible for the greater abundance of bacteria often associated with the finer sediments. ZoBell (1943) found that bacteria! multiplication and survival were enhanced by solid surfaces. The small clay and silt particles ( 1-2 mi· crons), with more surface area, support a larger bacterial population than coarse sands (Wood, 1953). Oppenheimer (1960) gave an account of bacteria! activities of sediments of shallow marine bays. In half of the sediment cores analyzed by Anderson (1939), the surface carbon was decomposed easily and the rate of decomposition decreased gradually with depth. In other cores, organic matter which was buried in anaerobic conditions, was much more easily decomposed. Thus the amount of organic matter available to bacteria varied within the sediment profile. Microbial decomposition of organic matter was not always greatest in the surface layers. Usually, a small fraction of buried organic matter is re­sistant to microbial decomposition. The refractory material (humus) is composed pri· marily of a ligno-protein complex and a hemicellulose-protein complex (Waksman, 1933). The decomposition coefficient ( degree of decomposition of total organic matter) was compared by Bader (1954) with the density of pelecypods in sediments. An extraction method was used to measure non-refractory organic matter. Pelecypod numbers were found to increase when the per cent of non-refractory organic matter increased. Thus, the amount of available organic matter may be significant to the support of populations of organisms which utilize the particulate organic matter in sediments. Methods CoLLECTION AREAS Red Fish Bay, partially shown in Fig. 1, is a shallow marine hay of the Central Texas Microbial Decomposition o/ Organic Carbon in Surface Sediments Gulf Coast, having an average water depth of 0.6 m and a high degree of plant pro­ductivity. Daily and semi-daily tides have little amplitude, less than 15 cm. The effec­tive tides in the Bay are more dependent upon wind direction, and the tidal influence may have a duration of one to several days. Seasonal differences in sea level create higher water levels in the spring and autwnn months. Little fresh water enters the Bay, and the nearest source of Gulf sea water is from Aransas Pass through the Barrier Is­lands, approximately 8 miles distant. The salinity may vary from 7 to 28 %o depending on rainfall. The mean monthly temperatures are difficult to evaluate because of the large variation. For example, in January 1958 the average temperature was 14ºC, while the minimum-maximum was 7-23.3ºC. The April average was 23.3ºC and the minimum­maximum was 14.5-33ºC. Spring usually occurs in March or late February. Four field stations (Fig. 1) were selected on the shores of Red Fish Bay and marked by metal stakes. Those stations were alternately dry or covered by water during wind driven tides. An additional station (No. 5) was located in an area in the Bay covered by approxi­mately 50 to 75 cm of water depending on wind. The area 1 marked by stake 1 was predominately a clay environment. The beach had a gentle slope, and the quiet water allowed the finer suspended material to settle out. Sea grass lay'ers and alternating oxidized or reduced zones were found in the sediment profiles of this field station. Station 2 was located in an area of coarser sediments where water movement was greater. The profile of station 2 was more homogeneous, and no sea grass fractions or zones of reduction were observed. Abrupt changes in the texture of the sediment were often noted in the profile. Alternating layers of sand, shell, and spotty areas of ferric hydroxide deposition were noticed. At station 3 clay minerals predominated in the subsurface sediments, while the surface layers had a coarser composition. The sediments were highly compacted, and profiles contained buried sea grass layers and distinct oxidized or reduced zones. Station 4 had a high shell content, which often comprised 75% of the sample. Sediments of the hay station 5 were predominately clay with severa} sea grass layers in a profile. The sediments were usually reduced below 2 cm and hydrogen sulfide gas was detectable. . DIRECTIONS FOR LocATING STATIONS A road log for field stations 1 and 2 starts in Aransas Pass at the intersection of state Highway 35 and Farm Road 632. Farm Road 632 (South Commercial Street) is followed for 0.9 mile to the intersection with Ransom Drive. The road log continues east on Ransom Drive for 0.55 mile. Field station 1 is located '1'26 yards from Ransom Drive on the Bay shoreline. Stake ·2 is placed 235 yards east of Stake l. A road log for stations 3 and 4 starts in Aransas Pass al the intersection of State Highway 35 and Farm Road 632. South Commercial Street (Farm Road 632) is followed for 1.7 miles to the inter· section with East Beasely Street. The road log continues east along Beasely Street for 0.95 mile. Stake 3 is approximately 0.15 mile southwest from the road. Stake 4 is 76 yards southwest of stake 3. The hay station 5 is 1.25 miles north from the causeway and 0.4 mile east of the mainland shore. CoLLECTION OF SAMPLES A wedge-shaped portion of sediment was removed from each shore station, bisected lengthwise, and distinct sedimentary layers were transferred to sterile sample jars and transported to the laboratory. Areas selected included aerobic, anaerobic, sand, shell, clay of various mixtures, and layers of decaying sea grass. The depth of the sedimentary layers was recorded. Samples were not collected from sediment depths exceeding 20 cm. Microbial Decompositwn o/ Organic Carbon in Surface Sediments Samples were collected from station 1and2 on the same day, while the next day stations 3 and 4 were sampled. The hay sediments were collected in a plastic tube which was pushed into the sedi­ment. The plastic tube was then filled with water, the top of the tube stoppered, and the water and sediment filled tube withdrawn from the sediment. A rubber stopper was placed in the b-0ttom of the tube, and the column of sediment was forced to the top of the tube. Sedimentary layers were removed to sample jars. PRESERVATION OF SAMPLES Sediment samples were refrigerated at 4ºC except for short intervals when aliquots were removed for the analyses. Carbon was determined within four hours after collec­tion. After 40 days incubation at 4º C the carbon was redeterrnined. The anaerobic sediments did not remain in the anaerobic state because of the storage conditions and the necessity for thorough mixing of the total sediment befare aliquots were removed for analysis. AEROBic BAcTERIAL PLATE CouNTs One gram aliquots of the sediments were removed from the sample jars befare re­frigeration and transferred to 75% sea water dilution blanks. The highest dilution used for plating was 1 :1,000,000. ZoBell's medium 2216 plus 1.5% agar (ZoBell, 1946) was used for estimating the aerobic bacteria! population of the sediments. Two dilu· tions were plated in duplicate, and the plates incubated for a week at 23°C. M1cRoscoPIC ExAMINATION Slides were prepared by mixing a few milligrarns of sediment with a drop of sea water. A cover slip was then touched to the edge of the drop, permitting a flow of liquid under the cover slip by capillary· action. Five fields were examined by phase contrast microscope and the variety of microorganisms tabulated for each sedimentary !ayer. WATER CoNTENT The sediments collected in the sample jars were mixed thoroughly. An aliquot be­tween 1 and 5 grarns was removed and transferred to a tared porcelain crucible, and the sediment weight determined with an analytical balance. The crucibles were heated at lOOºC for 18 hours, removed from the oven, cooled in a dessicator, and reweighed to determine water content. Duplicate analyses were made. All carbon values are % dry weight. ÜRGANIC CARBON DETERMINATION The organic carbon content of the sediments was determined by wet combustion using Corcoran's ( 1957) modification of the Krogh apparatus (Fig. 2). The sediment to be analyzed was thoroughly mixed in the sample jar. A weighed sarnple, containing between 1 and 10 milligrams of organic carb-On was transferred to reaction flask (A). Two and one half ml of 50% phosphoric acid was added to the com­ bustion vessel to convert carbonate carbon to carbon dioxide, which was then flushed from the train by a stream of oxygen. After 20 minutes all the carbonates were removed. A-reoction flosk B-hologen wosh e-600° e furnoce D-obsorption flosk e A B D F1c. 2. Micro apparatus for measuring organic carbon in sediments. The oxygen supply was cut off, and 5 mi of the oxidizing agent was added to the sedi­ment from a reservoir attached to the top of the reaction flask. The oxidizing agent was a mixture of 16 g potassium dichromate, 48 g of silver dichromate, and 500 mi of concentrated sulfuric acid. The system was again slowly flushed with oxygen, and the reaction vessel heated at a constant temperature of SOºC for 30 minutes. The oxygen carrying the carbon dioxide and monoxide passed through the halogen wash (B), cop­per oxide catalyst (600ºC) (C), and was slowly bubbled through 10 mi of the baryta solution in the receiving arm of the absorption flask (D). Flask (B) contained 5 mi of a halogen wash, composed of 20 g of potassium iodide, 50 mi of 10% sulfuric acid, and 1 g of powdered antimony. The halogen wash was employed to trap any escaping chlorine as antimony chloride. Any carbon monoxide from incomplete combusion was converted to carbon dioxide by the copper oxide catalyst at 600ºC. The baryta solution was a mixture of 1 part saturated barium nitrate solution and 2 parts saturated barium hydroxide solution, diluted to 0.lN. At the end of the combustion period the absorption flask was removed from the train, and the exces.s barium hydroxide titrated with O.IN hydrochloric acid. The difference in the titer between the original baryta solution and the final solution was proportional to the amount of organic carbon contained in the seliment sample. With this method 1-10 mg of organic carbon can be measured with an approximate error of 1 %. Corrections were made for water content of the sediments, and the organic carbon reported on a dry sediment basis. The organic carbon was redetermined after 40 days storage at 4º C. A 40 day storage period permitted an almost complete decomposition of organic matter. At the end of 40 days bacteria! activity had either ceased or proceeded at a very decreased rate. Refrig­eration at 4ºC closely simulated the environmental conditions found in thc sediments during the winter period. The loss in carbon after the 40 days storage at 4ºC was as­sumed to be proportional to the amount of bacteria! activity in the sediments. GRAIN SIZE ANALYSIS Grain size was estimated with 5 sieves of standard Tyler screen sizes. Originally de­signed for field use, the apparatus consisted of 5 screens, 1 inch in diameter, mounted in a plastic tube and arranged 2 inches apart in descending order of pore size. The dis­ Microbial Decompositwn o/ Organic Carbon in Surface Sediments lance between the screens was marked by 20 equal divisions etched on the plastic tube. An aliquot of sediment was measured in a calibrated plastic cup and transferred to the upper screen. The apparatus was constantly agitated and sea water added to facilitate division of the sample into the component grain sizes. The per cent of diffcrent sized particles in a sample could be estimated by comparing the levels of the material collected on the various sieves with the lines etched on the plastic tube. The silt and clay fractions of the scdiments were not retained by the sieves. The material collected on the first two screens was composed of shells, shell fragments and sea grass. The siews used had the following Tyler screen sizes: 1, greater than 1 mm; 2, coarse sands with diameters between 0.5 and 1 mm; 3, sands with diameters between 0.25 and 0.5 mm; 4, fine sands with diameters between 0.125 and 0.25 mm; and 5, very fine sands with diameters between 0.062 and 0.125 mm. Results Twenty·eight sediment profiles are presented histographically and grouped according to station in Fig. 3 to 10. The four histograms on each sediment profile represent the same sample. and each bar denotes a sedimentary layer. The top bar is the surface layer of the profile, and the depth in millimeters for the other sedimentary layers is placed opposite the appropriate bar. The results of a preliminary survey of the sedimentary emironments along the shores of Red Fish Bay are presented in Fig. 3. Bacteria) counts are not recorded for these samples. The seasonal change in organic carbon is presented in Figure 11. Two field stations 1 and 2 (Fig. 4-7) have been sampled monthly from October through April to include both a clay-sand and sand-clay environment in the seasonal study. The average initial carbon and carbon after 40 days storage is graphed for the two field stations. The types of bacteria found in the shore sediments ( stations 1--4) show a slight change with the seasons, whereas those in the Bay at station 5 ( Fig. 11) had no ap­parent change. At stations L 2, 3, and 4 rods were predominant in October; rods and cocci \""owmber through February; and spirilla, rods, diplococci, and cocci in March and April. At hay station 5 spirilla, rods, diplococci, cocci, and vibrio were predomi· nant October through April. Seasonal variations in counts of bacteria are presented in Table l. T .WLE 1 :\Iinimum bacteria! populations in sediments from Redfish Bay, Texas, as determined by standard plate count procedure. :\lillions per gram of wet sediment. Are-al Area 2 !dooth SurÍaC'e 1 C'nl Suríu:e !cm October 5.7 1.5 ClioYember 0.5 0.2 9.6 Dec:ember 2.7 1.7 8.4 19.0 January 1.8 LO 5.5 4.2 February 5..l 8.0 6.5 1.3 :\larc:h 25.0 49.0 16.0 l.7 ..\pril 55.0 7.5 49.0 9.0 June l-10.0 70.0 July 100.0 2.0 70.0 100.0 _.\ugust 150.0 10.0 200.0 1.0 SEOIMENT PROF ILE O dtpth in m:n r-~=11~~.----------,I F~ O Q5 IO 15 20 25 3.0 35 O 102030 405060708090 •¡. orQonic corbon "'!. loss in or9onic corbon ofler 40 doys ot 4•c no! meosured o 1 2 3 4 5 6 7 8 9 O IO 20 30405060708090 X 10 º/• sond , shell , s'o 9ross, cloy oerob1c bocteriol populotion o lk3l ~ CJ SEOIMENT PROFILE depth in mm 1 =~ =1~~.------1 ~ O Q5 IO 15 20 25 3D 35 O 10 20 30 40 SO 6070 8090 0/o or9onic corbon °/o loss in OrQonic corbon ofter 40 doys º' 4° e not meosured 1~~=~=~~:';:;:::::~:r.~-~: :1'f ,1 o 1 2 3 4 5 6 7 8 9 o JO 20 30 40 50 60 70 80 90 X 10 % sond, shell , ''º orass,cloy oerob1c bocteriol populotion E:J ~ im CJ SEDI MENT PROFlLE depth in mm o'""".-~~as ts~~20~~2~5~~30~~3~,I ~~ ~~~1o~~,-10-20-30-4o_so_60_1_0_0_0_90~1 0/o orgonic corbon º/• loss in on;ionic corbon ofter 4 0 doys ot 4°C no! meosured o 1 2 3 4 5 6 7 8 9 X 10 oerob+c bocteriol poputotion F1G. 3. Analysis of sediments during prelimi· nary survey October 1958. 'Surface sediments collected between areas 1 and 2. Discussion Monthly profile samples of the shoreline sediments m Red Fish Bay collected from single stations show considerable differences in texture and placement of oxidized and reduced zones. The variations in sediments within short lateral and vertical distances make it diflicult to compare the data obtained. However, the uneven sediment distribu­tion is significant for understanding microbial activities in sediments and the subsequent diagenetic processes taking place. Our data indicate that microbial activities are related to the available organic matter. The uneven distribution of the organic matter may thus be a primary factor in the fonnation of varied microfacies. Microbial Decomposition o/ Organic Carbon in Surface Sediments F1G. 4. Analysis of sediments from station 1 during (a) and (b) October, (e) November and F1G. 5. Analysis of sediments from station 1 during (a) January, (b) February, (e) March and (d) April 1959. . SEOIMENT ~ IL~1 O D.5 LO 1.5 20 2.S 3.0 3.5 •¡., oroonic corbon not meosured 01 23456789 X 10 oerob1c bocter iol populolion SEDIMENT PROFILE depth in mm .-­ fa ------,1 J~ llílíllllllJ O Q5 ID L5 2.0 2.5 3.0 3.5 •¡. oroonic corbon ~------------'I ~ O 1 2 3 4 5 6 7 6 9 X 106 oerob1c bocteriol populotion (d) January, 1958. SEDIMENT depth ....-----1 ~ ~ . 0~0-5,---IO--L5,.--,2!l--2.5:-:3D..,.--,,l5.,-' •¡. oroonic corbon r 0 123456789 X 106 oerobic bocteriol populotion SEOIMENT deplh .---t ------,1f~ .­ .-------~! O~-Q-5,---IO--L5---:-2-P-2.5=--:~-:0---:-l57"' O 10 20 30 40 SO 60 70 80 90 º/• oroonic corbon °/o loss in oroonic corbon ofter 40 doys 01 4°C ~1•:>'3 O 1 2 3 4 5 6 7 8 9 O IO 20 30 40 50 60 70 80 90 X 107 •;. sond, she11, seo 9ross,cloy oerob1c bocter iol populolion O ~ ~ L=i '------------' O 102030405060708090 °/o toss in on;ionic corbon ofter 40 doys 01 4°C 1 · 1JW:F(~ o to 20 30 40 50 60 70 80 90 •¡., sond , shell, seo 9ross, e lay D ~ IWil CJ O !02030405060708090 •¡., loss in oroonic corbon ofter 40 doys al 4°C 11wn ~f1 l O IO 20 30 40 50 60 70 80 90 º/• sond , shell, seo oross ,ctoy ES] lll!SJ !m c:::=i PROFILE in mm ,~~ ~~~ ----, ~~ 150 ~ ::: O 10 20 30 .t:IO 50 60 70 80 90 •¡. loss in or9onic corbon ofler 40 days ot 4°C O IO 20 30 40 50 60 70 80 90 •¡. sond, shell, sto gross ,cloy c:J 0;J ~ CJ PROFILE in mm SEOIMENT PROFILE b not meosured 0 123456789 X 10 oerobic bacteriol poputotion SEDIMENT depth ~ O 0.5 10 l5 20 2.5 3.0 º/• OrQOnic corbon rr O 1 2 3 4 5 6 7 8 9 O IO 20 30 40 50 60 70 80 90 x 106 % sond , shell, sto oross, cloy oerobic bocleriol populotion CJ ~ ~ c::J SEOIMENT depth ~------,1 b o'-o-5_1_P_L5__,.2!l--2.5:-:3D..,.--,.357"' º/. or9onic corbon O 1 2 oerob1c =r O Q5 % , 0 123456789 X 107 oerob1c bocteriol populotion 1 1 3 4 5 6 7 8 9 x 106 bocleriol populotion SEOIMENT deplh =1 LO 1.5 20 2.5 3.0 3.5 or9onic corbon 1fg .,------------, 3.5 O 102030405060708090 º/• loss in orqonic corbon oflet 40 doys ot 4°C 1 li,\:; ;);; ;i;1 l 11;::¡1:1~r:::z¡ ~ o 10 20 30 40 50 60 70 80 90 º/. sond , shell, seo oross, cloy [3]~~0 PROFILE in mm PROFILE b in mm o ~~---­ 10 : : : 15 --­50 --­ 120 --­ o 10 20 30 40 50 60 70 80 90 º/• Ion in or9onlc corbon ofter 40 doys ol 4° e !~mfil:E:L O IO 20 30 40 50 60 70 80 90 % sond, shell, seo 9ross,ctoy Q ~ ~ CJ PROFILE in mm ,~&~­ O 10 20 30 40 50 60 70 80 90 º/• loss in or9onic corbon ofler 40 doys ot 4° e EJ!m~D Microbial, Decomposition of Organic Carbon in Surface Sediments SEOIMENT PROFILE o SEOIMENT PROFILE ..-.."ji...1,...-----....::...,""j hMlllil1 o Q5 lO l5 20 25 3.0 3.5 o 102030405060708090 o 0.5 lO l5 2.0 2.5 3.0 3.5 o 102030 405060708090 •¡. or9onic corbon -t. loss in or9onic corbon of1er º/o or9onic corbon "º Joss in or9onic corbon ofler 40 doys 01 4°C 40 doys ot 4ºC 11 .....__1 ~ ¡,; ; .~t,~~ ~ ___________,¡ j 1 O l 2 3 4 5 6 7 8 9 O IO 20 30 40 50 60 70 80 90 0;:---:1--.:-2---::-3_4_5_6-,-8--.-J9 o 10 20 30 40 50 60 70 80 90 X 106 º/o sond, shell, seo 9ross ,cloy X 106 /. sond, shell, uo 9ross ,cloy 0 oerotllC boc1e11ol populolion [=:J ~ ~ C::J oerob1c bocteriol populolion D ~ ~ C::J SEOIMENT PROFILE SEDIMENT PROFILE d d•pth in mm deplh in mm .-----~-¡ t ~~~ ­ r .-----­ ------,j,Iº----~l,t~!~ O Q5 ID 1..5 20 25 30 3.5 O I02030 405060708090 O 05 ID l5 2!> 25 l.O 3.5 O 102030405060708090 % oroonic corbon "º loss in or9onic corbon ofter •¡. or;onic corbon •1. loss in oroonic corbon ofter 40 doys 01 4• e 40 doys º' 4• e fI1:1~I;~:~~1Jfü1 ....:.. ; j O 1 2 3 4 5 6 7 8 9 O IO 20 30 40 50 60 70 80 90 01234 56789 O 10 20 30 40 50 60 70 80 90 X 106 •1. sond , shelt, seo 9ross, cloy X 106 •1. sond, shell, seo oross ,cloy oerobic: bocleriol poputotion fITD ~ mJ !=1 oerobic bocteriol populotion c:J elil~ CJ F1G. 6. Analysis of sediments from station 2 during (a) October, (b) November, (e) December and (d) January 1958-S9. DISTRIBUTION OF ÜRGANIC CARBON The organic carbon content of various sedimentary types and layers is not homog­enous over the limited areas studied. Sediments, separated by a few centimeters in depth or lateral area, differ appreciably in their carbon content. The type of deposited organic matter, texture of the sediments, time of year, and depth of sample are sorne of the fac­tors which a:ffect the residual concentration of organic carbon in the sediments. The carbon content of a sediment profile does not decrease consistently with depth of sampling. In slightly more than half of the shore profiles, at least one subsurface sample contains more organic carbon than the surface layer (sediment profiles: Figs. 3b, 3c, 4a, 4d, 5a, 5b, 6b, 8a, 8b, 8c, 9c) . Where an increase in carbon with depths was found, the sedimentary !ayer was usually associated with either a sea grass fraction or a high shell content. The station 2 area, which had the most homogeneous profile, usually showed a steady decrease in organic carbon with sample depth. The hay samples had organic carbon contents up to 3.5%, a concentration approxi­mately two times higher than the October surface shore samples and ten times higher than the winter values. The sea grasses in the surface hay samples account partially for the high carbon values. The subsurface layers of the hay samples appear to have large amounts of refractory material. During the winter months when carbon values below 0.1 % were recorded for the shore samples, the hay sediments had subsurface carbon values of approximately 1 %-The sediments there may have hada more stable environ­ment than in the shore areas thus accounting for the large amount of organic matter. Sea grass entrapped in the sediment accounted for an appreciable amount of the or­ganic carbon measured, but seemed quite refractory to bacteria! activity. Coarse sea Microbial Decompositwn o/ Organic Carbon in Surface Sediments SEOIMENT PROFILE deplh in mm r~~1~gt~~~~­ o Q5 lO l5 2.0 2.5 :iO l5 O 102030405060708090 •t. or9onic corbon "t. loss in orgonic corbon ofter 40 doys ol .q• e bll0 1 ¡:·:·:·:·:·:-:-:'.....}.. , ~ . : '····" j L-----~--~­ 0t23456789 O 10 20 30 40 50 60 70 80 90 X 106 "'!. sond , shell, sto 9ross ,cloy oeroDIC bocteriol populolion CJ !B:n ~ CJ SEDIMENT PROF1LE depth in mm ~t -1~~~­ 0L--Q-5-IP-l5-c2!l-25--3.0:-:-357' O 10 20 30 30 35 o 10 203-0 405060708090 •¡. oroonic corbon "lo loss in or9onic corbon oft er 40 doys ot 4°C O 1 2 3 4 5 6 7 B 9 O IO 20 30 4 0 50 60 70 80 90 x 10 7 ~·. sond , shell, sro 9ross, cloy oerotuc bocter iol populotion § ~ ~ c::::::J F1G. 7. Analysis of sediments from station 2 during (a) February, (b) March and (e) April 1959. grass was quite common in Redfish Bay and therefore it was difficult to relate sediment size to the decomposition of the other less refractory types of organic matter. It was impossible with the procedures used· to separate the sea grass from the other organic matter. EFFECT OF SEDIMENT TYPE ON BACTERIAL DECOMPOSITION OF ÜRGANIC CARBON Organic matter in the coarser sediments appeared to be more easily decomposed than organic matter in the finer sediments. Sediments with 40-50% coarse-grained material show a 58% loss in carbon after 40 days, while samples with 80-98% coarse material hadan aYerage loss of 89%. Severa! factors might explain the slower rate of decomposition and loss of carbon oh­ SEOIMENT PROFILE O d1pth in mm ~-1~1~­ llC= ;:: O 0.5 10 1.5 20 2.5 30 35 O 102030<05060708090 •¡. oroanie corbon •¡. loss in or9onic eorbon ofhr 40 doys O! 4• C ....-: 1 0123456769 X 101) •¡. sond, shell, seo 9ross,cloy oerob1c bocteriol populotion [TI (z::J lm CJ SEOIMENT PROFILE b depth in mm =k=i~~~.. ­ 0 0.5 l.O L5 20 2.5 30 35 o 102030405060708090 º/• or9onic corbon •t. loss in orgonic corbon ofter 40 doys ot 4° e ....., O 1 2 3 4 5 6 7 8 9 x 106 % sond , shell, seo oross, cloy oerobic bocteriol populotion Q1J ~IWíl CJ SEOIMENT PROFILE deplh in mm ~ir ~lrh~E ­ 0~05--IO-l.5-2:-D--:-2.5~30c:--:3c::-'5 O 10 20 30 econd blue crab experiment . ..\11 values are in m:\1/1. Crab nuid ::'\a i;;: Ca Ms a so, To1al molar c:onc. l. Blood í74 14.6 17.5 52.5 89.J. 15.5 1768 :\ledium 12"25 40 22 128 1420 69.5 2935 2t Blood 161 6.9 3..2 12.5 188 6.1 378 :\ledium 23 0.8 0.5 2.1 27.1 0.7 54 3:t: Blood 666 15.0 11..J. 46 722 8.6 J.169 :\ledium 899 20.l 19 . .J. 102 1041 52 2134 4§ Blood 688 13.5 11.9 58.5 780 11.l 1563 :\ledium 968 21.6 20.6 110 1118 5.J. 2477 • Lapma crah !-ample'd allrr 2.t bours in !Df!'dium shown and 120 bow-s in (O} more lhao 970 mM/I. t Rinr crah a her 96 bours in mnlium !-bo...-o. : Rh·rr crab aftrr 79 houn in !IW'dillm sho...-n . § La~na crab altrr 79 bo~ in mrdium sho•-o. llrdia for uabs 3 a.nd 4 .,.,.ett ~parat~ly pr~pared by dilution &om • oonttn· trated slock solut.ioo . Osmotic and /onic Regulation in the Blue Crab and the Ghost Crab ll5 and 29 Laguna crabs (captured in 51 %e) were transferred to tanks of normal sea water (36-38 %e). Fourteen of the river crabs died within 36 hours, seven of the remaining TO were still alive in December and were used in this experiment. There was no immediate mortality among the Laguna crabs, but all of them were dead in December and an at· tempt was made to capture more Laguna crabs to replace them. Crabs were very scarce in the Laguna at that time, and survival in the laboratory was poor, even among crabs kept in dishes of the water in which they had been captured. Analyses of body fluids and media sampled at the time of capture of sorne of these crabs (Table 13) showed that TABLE 13 Results of analyses of body fluids and media during winter (Dec. 1956) for Laguna Madre C. sapidus sampled immediately after capture. Ali values in mM/ l. Crab Fluid Na K Ca Mg CI so. Total molar conc. 1 B 704 '14.9 15.9 55.3 782 16.0 1578 M 790 16.1 2'2.0 80 925 46.6 '1880 2 B/M B 0.89 614 0.93 14.4 0.72 14.0 0.69 52.5 0.85 611 0.34 10.8 . . . 13'16 M 735 16.5 '13.9 68.9 815 40.2 1690 3 B/M B 0.84 529 0.87 10.9 1.01 '10.0 0.76 39 0.75 612 0.27 1'1.2 1212 4 B '524 9.2 9.8 37 608 11.8 1200 5 B 485 13.1 11.6 35 6'18 14.1 1212 M 608 11.4 12.I 67 690 35.5 1399 6 B/M M 0.84 78'2 0.97 15.8 0.85 20.2 0.55 88 0.89 894 0.28 46.2 0.86 1845 u 838 15.4 15.4 48.4 829 26 1773 B 786 16.4 16.9 53.0 814 11.9 1698 7 B/M u 1.0 822 1.04 17.8 0.84 25.4 0.60 87.5 0.91 0.26 B 802 18.6 20.0 56.0 911 9.7 1817 CFI 863 14.4 30.5 1'20 %8 89.3 2085 B/ M 1.03 'l.18 0.99 0.64 1.02 0.21 five out of seven were regulating all ions to sorne extent. Magnesium, and especially so4, were well regulated in all of them. Seven Laguna crabs were brought gradually to normal sea water and were held there with the seven river crabs for a one week control period. Blood and medium chloride concentrations at the beginning and end of this period are given in Table 14. AH crabs were then transferred to hypersaline water ( 61 %0 ). Survival times (Table 15) were much shorter among the Laguna crabs, three of which were killed during fluid sampling. Analyses of body fluids of these crabs at various times after application of hyper-saline stress (Table 16) show that while there were differences in the rates of increase of blood TABLE '14 Mean chloride concentrations in mM/l of crab blood and medium during the control period of the third blue crab experiment. The number of individuals is indicated in parentheses Blood Date Sea water River crahs* Laguna crabsf 1'2/ 22/56 533 519 (7) 551 (6) 12/27/56 543 531 (6) 552 (4) • Collected at 13%0 and acclimaled three months al 38%o· t Collecled al 43-SB%o and gradually transferred lo 3B%o· TABLE 15 Survival time of Callinectes sapidus transferred from 38%0 into hypersaline water, 61%0 No. of eraba Survival time (hr.) Guadalupe River crabs• 7 100 to 230 Laguna Madre crabst 8 48+, 12, 22, 48, 48, %+, 112+ * Collecled al 13%0 and acclimaled three months at 38%o· t Collected al 43-58%0 and acdimated one wcek al 38%o· t Three killed drawing gul fluid. TABLE 16 Average concentration of ion in media and body fluids of Callinectes sapidus from the Guadalupe River* and Laguna Madret under hypersaline stress of transfer from 38%0 into 61%0 (at Otime) . Concentrations are in mM/l. No. o{ Time Group crabs hr. Na K Ca Mg Cl so, Total molar conc. MEDIA o 470 9.9 10.2 53.5 544 28.0 1116 '168 865 18.6 18.5 98 1033 51.5 2056 BLOOD River 5 o 456 9.2 13.7 37.5 515 7.3 1039 1 26 598 13.3 19.4 51.5 681 19.1 1362 1 62 63'4 10.3 14.7 56.7 710 13.l 1439 4 168 830 '19.3 21.9 74.8 940 23.'2 1909 Laguna 3 o 4841 8.1 13.1 41.2 588 8.7 1143 1 27 726 14.8 '20.4 60.0 843 13.5 1678 1 55 7':12 '10.2 20.8 58.0 920 11.6 1812 1 96 922 19.6 21.6 61.0 1002 24.4 2074 1 192 863 20.6 21:2 66.0 938 20.3 1929 RATIO OF BLOOD TO MEDIUM River 4 168 0.96 1.04 l.'12 0.76 0.94 0.45 0.93 Laguna 1 192 'LOO 1.16 1.08 0.67 0.94 0.39 0.94 URINE River 5 o 470 10.1 12.9 39.3 530 32.3 1100 1 26 646 '16.2 21.4 52.0 720 46.6 '1502 1 62 690 17.4 22.6 79.8 690 67.5 1567 4 '168 808 22.5 26.5 90.5 912 84.6 1944 Laguna 3 o 521 9.1 16.1 49.9 544 60.9 '1'202 1 27 728 13.3 27.2 104 826 77.5 1776 1 55 844 16.3 26.4 80.5 936 8'2.5 1986 1 96 831 17 23.9 '108 903 93.0 1976 1 192 832 '26.1 '25'.2 l'Z2 925 96.2 2027 RATIO OF URINE TO BLOOD River 4 '168 0.97 1.17 1.21 l.'21 0.97 3.65 1.02 Laguna 1 192 0.96 '1.27 1.19 1.85 0.99 4.74 1.05 STOMACH FLUID River 2 o 520 11.6 12.0 44.7 566 21.1 1175 1 '26 724 1'4.7 15.8 76.5 ln5 37.8 1684 1 62 687 11.9 '22.8 '101 872 33.2 1611 4 168 842 19.0 '22.0 108 962 45.0 1998 Laguna 1 o 507 9.3 11.4 45.0 546 32.l 1151 1 55 892 '10.8 20.4 68.5 935 31.5 1958 RATIO OF STOMA:CH FLUID TO BLOOD River 4 168 1.01 1.01 1.04 1.64 1.02 1.94 1.05 1 55 1.13 0.94 0.98 1:18 0.98 2.71 0.925 • CollecLed al 13%0 and acclimaled three montha at 38%o· t ColJecled al 43-58%0 and acclimated one week al 38%o· concentrations hetween the two groups, hloods of the four river crahs and one Laguna crah which survived 7 or 8 days were nearly identical. Sulphate, and to a lesser extent, magnesium, were the only ions heing regulated. Concentrations of these ions were higher in stomach fluid and urine than in hlood. Discussion The results of this work support the findings cited in the introduction that hoth semi­terrestrial and certain estuarine crahs are capahle of hypo-osmotic regulation. Oeypode and Vea on one hand, and Callineetes on the other, are similar in that they can all withstand hoth high and low salinity stress for long periods, hut they differ in the mechanisms used. The hlue crah occurs naturally in waters where salinities of 58 %o (150% S.W.) may persist for months. lt lives immersed, and gill ventilation and stress are more or less continuous. It accomplishes this by allowing blood concentrations of Na, K, and Cl (and presumably osmotic concentration) to rise (B/M ratios vary between 0.7 and 1) , while hlood concentrations of Mg, and to a greater extent, SO,, are held clown (B/M ratios of 0.5-0.7, and 0.2-0.3, respectively) at least in part by excretion in the urine and con­centration in the stomach fluid. Response to application of even greater stress in the lahoratory was similar, for Laguna crabs, although duration of stress was only 3-7 days. In one case (Table 5, crah No. 1) a Laguna crah was alive and active with blood concentrations of the major ions ahout equal to their concentrations in 150% S.W. In Vea and ocypode response to high salinity stress diflers from that of Callineetes in that hlood Na, K, Mg, and CL and prohably as a consequence, blood osmotic concentra­tions, are well regulated (B/M ratios from 0.4-0.7) while Ca and SO, are not regulated as well as they are in Callineetes. Although intracellular electrolyte concentrations have not heen studied in any of these species, it would seem that Vea and Oeypode do most of their regulating at the boundary hetween hlood and medium, while Caleineetes main­tains lower gradients at this boundary and either maintains another series of gradients hetween blood and cells or tolerates large fluctuations in intracellular concentrations. Studies of the type done by Shaw (1955h) on fluctuations in concentrations of intra­cellular electrolytes in Carcinus might Yery profitably he extended to Callineetes, which has a wider range of hlood concentrations. Such studies might provide information about hoth the activity of cell memhranes in ionic regulation and ahout the effects of fluctu· ations of intracell u lar electrolytes on cell function. In Pachygrapsus (Prosser et al., 1955) the degree of regulation of various ions (ex­pressed as per cent change from hlood concentrations in 100% S.W.) rnries with the direction of the applied stress (Table 17). This also appears true of Oeypode, Callinectes and Palaemon serratus. In Callinectes the order of decreasing regulation is exactly re­versed on going from dilute to concentrated sea water. The two studies on Paehygrapsus (Prosser et al., 1955; Gross, 1959) agree as to the order of decreasing regulation in dilute water, and except for Na, also agree in concentrated water. Difference in degree of regulation might be due to the manner in which stress was applied. There is no agreement, either as to order or as to degree, between the three species. This variation in Pachygrapsus was interpreted by Prosser et al. as showing that hypo and hyper regulation are fundamentally two different processes. An extension of this deduction is TABLE 17 Regulation of ions in crabs during transfor into concentrated and dilute sea water. Values are per cent change from blood concentrations. loto dilute sea water loto concenlraled &ea water Species Per cent S.W. Na K Ca Mg O S04 Per cent s.w. Na K Ca Mg Cl so. Pachygrapsus * Ocypode Ocypodet Callinectes 50 -33 -31 -25 -70 14 -16 -10 -20 -23 -15 -7 50 -18 ·-10 -18 -32 5 -65 -25 -77 -33 -64 -17 170 '190 150 185 44 28 21 82 44 84 38 111 8 69 23 60 13 186 36 99 19 83 190 218 Paleomonetest 50 -40 -13 +12 -12 -30 -56 120 20 33 19 64 15 23 • Prosser et al., 1955. t G'º"· 1959. l Pany, 1954. that ionic regulation depends on separate transport systems which either are not re­versible or which do not work with equal efficiency in both directions. Examination of the internal vs. external concentration curves for the different ions reveals that they cross the isotonic line at different points. In Ocypode, as externa} concen· tration increases, K and Mg regulation reverse at 60% S.W. Osmotic and total molar concentrations, Na (at 12-25ºC), Cl, 504 regulation reverseat around 100% S.W.; Na (at 29-35ºC) reverses at 110% S.W.; and Ca regulation does not reverse until externa} concentration reaches 180% S.W. It would seem that the concentration of each ion, or at least group of ions, is controlled separately, and that the different ion pumps can be running in different directions at the same time. In spite of this variation in the handling of various ions, the ratio of total anions to total cations seems to be relatively constant for a number of Decapad crustaceans. V alues calculated from blood analyses of several kinds of Decapods are presented in Table 18. Six of the twelve values fall between 0.958 and 0.963, agreement within 0.5%. Ali of the values outside of this range are for animals that were maintaining large ionic TABLE 18 Ratios of constituents of bloods of marine Decapods in dilute, normal, and concentrated sea water Ratio of anion~ Cl*/Na• Ratio of osmolic No. of Per cent to cations• and and concenlraliont to total Species individuals sea water standard deviations standard deviations molar concentrationt Six Decapods (Prosser et al., 1950) 6 100 0.958 ± 0.020 1.091 ± 0.017 Palaemon serratus§ (Parry, 1954) 50 0.963 1.165 8-20 100 0.963 1.091 20 120 0.916 1:1411 Callinectes sapidus 20 5--258 0.961 ± 0.051 1.131 ± 0.041 Ocypode albicans 12-25ºC 11-12 14-197 0.962 ± 0.041 1.078 ± 0.082 29-35ºC 9 25-161 0.907 ± 0.057 0.963 ± 0.065 1.058 ± 0.106 After capture 15-20ºC 6 5 100 103-146 0.961 ± 0.019 0.983 ± 0.020 1.058 ± 0.015 1.069 ± 0.019 Cardisoma guanhumi 1 125 0.911 1.011 Uca pugnax & puglicator (Green et al., 1959) 100 1.290 1.637 0.994 175 1.23 1.53 0.940 • Tot11.l milliequivalents per liter. t Osmotic concenlration expressed in equh·alenls of N aCI as mM/ l. l Total o( the solutes determined expressed in mM/ l. § Calculated from mean ion concentrations. Osmotic and lonic Regulatwn in the Blue Crab and the Ghost Crab 119 and osmotic gradients under hypersaline stress; in the case of Ocypode combined with high temperature stress. In the cases where deviation occurs the ratio of anions to cations generally decreases; that is, the usual anion deficit becomes greater. Uca is exceptional in having an anion surplus instead of a deficit. V ariation in the ratio Cl/Na parallels that for anions to cations. Chloride is relatively less concentrated in blood than in sea water (where Cl/Na is near 1,164), although in absolute concentration there is still more chloride than sodium. There are several ways that the electrical balance may deviate from unity such as with undetected solute (anionic in all but Uca) with blood proteins carrying an electri­cal charge at blood pH, or with the binding of ions in undissociated complexes. Changes in the ratio may occur with addition of unidenrified solute, or by change in blood pH. One way of detecring unidentified solutes in the blood is by comparing osmotic con­centration (O.C.) with total molar concentration (T.M.C.) of determined solute. Rarely are all the necessary measurements made on one animal. In the case of Ocypode at 29­35ºC the average ratio O.C./ T.M.C. for nine animals is 1.106, indicating that about 10% of the solute is not identified. The ratio of anions to catious averages 0.907, indi­cating that 9% of the anions have not been identified. The presence of undetected anionic solute seems likely. In Uca (Green et al., 1959) the ratio O.C./ T.M.C. is less than one, indicating that sorne of the salute is not osmotically active. Since there is an excess of anions, it may be that sorne of them are normally bound, either to proteins or in unionized cornplexes. The way in which these deviations are connected to hypo-ionic regulation is still unknown. Several semi-terrestrial crabs, but not Callinectes or Palaemon (Parry, 1954) , have been found to have low urine Na'concentrations. The conditions under which this occurs are not alway·s identical between species. This decrease in urine Na was first observed in Pachygrapsus (Prosses et al., 1955) , and confirrned for that species by Gross (1959). It .does not occur in low salinity, and can be reduced or abolished by removing Mg stress. In Ocypode it occurs at all salinities. at high temperature, but only in high sa: linities at low temperature. In Cardisoma it was found in one crab tested in 125% S.W. In Uca, (Green et al., 1959 and this paper) the decrease in urine Na is generally more pronounced and more consistent than in the other species. It occurs in both high and low salinities at all temperatures, and is minimal at interrnediate salinities. In both Uca and Ocypode injections of small amounts (30-50 micromoles) of Mg into the haemocoele are followed by temporary fluctuations in urine Na and Mg concentrations. The direction of the change in urine Na depends on its preinjection concentration, which in turn is a function of both salinity and temperature. The changes in urine Na and Mg (in milliequivalents per liter) are not equal. lt would seem that Mg excretion in­hibits Na movements in the antennary gland. That this is not the only cause of the decrease in urine Na, at least in Ocypode, is indicated by data presented in Table 19. All combinations of high and low urine Na and Mg can occur. The high anion to cation ratios indicate large amounts of undetermined cations in the urine. The role of this shift in Na excretion in blood regulation is still unresolved. In Uca, Green et al. found that urinary NH3, although high, did not completely rnake up the urine cation deficit. lt may be that high temperature increases production of sorne cationic rnetabolite which is excreted in the urine at the expense of Na excretion. lt was shown by Flernister (1958) that urine· production by Ocypode stops when water is unavailable. This was confirrned in this work by conrinuous withdrawal of urine TABl.E 19 Sodium (Na) and magnesium (Mg) concentrations in mM/I in blood (B) and Urine (U) of Ocypode under various conditions of salinity and temperature Ratio of aniona Cl in medium Temp. ºC Na Mg to cations 72 17 u433 27.5 '1.29 B 448 25.3 1.04 129 30 u 26 20.5 6.3 B346 36.3 0.867 840 29 u 83 '184 1.6'1 B 534 50.8 0.920 1036 17 U620 103 0.913 B662 64 0.969 from crabs in air. After initial drainage of the bladders and one hour exposure to air, Oeypode produces urine at rates between 10 and 40% of body weight per day. At two hours the rate is around 5% body wt per day, and by three hours urine formation gen­erally' stops. Crabs kept in air apparently form urine until the bladders are full and then keep it, for urine can usually be obtained from crabs kept as long as forty-eight hours in air. Exchange of harmful metabolites and Mg for the sodium in stored urine may be of adaptive value and does not conflict with the available data, but there is no proof for such a mechanism. Blood and urine samples taken from five ghost crabs captured on the beach (in De­cember at 20°C) differed from those taken from crabs kept in the laboratory. Urine concentrations of all ions but Mg were lower than blood concentrations, and even for Mg the difference was not great. The ratios of total mM/ L of determined solute in urine to total mM/ L in blood averaged 0.878 ± 0.102. The urines contained from 12 to 338 fewer mM/L than did the bloods (avg. 137 ± 123). Salt conservation by production of hypotonic urine was unnecessary and ineffective, because urine production had sup· posedly stopped. Bladder volume is small compared to blood volume, and other routes of salt loss ( except in feces) had been cut off. Although osmotic concentrations were not measured in these crabs, Oeypode kept in the laboratory had not demonstrated the ability to produce hypo-osmotic urine. Anion to cation ratios in the urines averaged near one, but the separate values were either below 0.92 or above 1.11. In order to be iso-osmotic to blood these urines would have had to contain from 12 to 338 mM/ L of unidentified solute, which from the electrical balance figures could have been either anions or cations. The effect of temperature on hyporegulatory ability was found to be of considerable importance in both Vea and Oeypode. At 25ºC or less, Oeypode survived for at least three weeks in 180% S.W., and blood osmostic concentration after ten days exposure was only a few per cent higher than 100% S.W. Blood concentrations rose somewhat in 197% S.W., but the crabs survived for 7-10 days. At temperatures between 29 and 35°C blood concentrations rose in all concentrated media, and the crabs only survived 4 to 5 days in 160% S.W. Controlled temperature experiments with Vea indicate that blood osmotic concentrations ( under equal hyper-saline stress) are better regulated at 21 ºC than at lOºC, and least regulated at 30º C. Neither species (Oeypode from Texas or Vea from Woods Role) withstood combined high salinity and high temperature. Oeypode retreated to its burrow, often with the entrance plugged, during the day in summer and during prolonged cold spells in winter. ltwas active during daylight at intermediate temperatures. The effect of temperature on salinity tolerance of C. sapidus from the Laguna Madre was not clear. The literature on the effect of temperature on severa} euryhaline Crustacea has been summarized by Kinne and Rotthauwe (1952) and by Verwey (1958). In the crab Erweheir, the amphipod Gammarus, and the prawn Palaemonetes, high tempera­ture appears to reduce regulatory ability. This has been shown in this paper to be true of Ocypode and Vea. Many estuarine forros migrate to the sea in winter, among them peneid shrimp (Gunter, 1950) from the coastal bays of Texas. Callineetes sapidus, on the other hand, has been reported to migrate from Texas coastal bays to the open Gulf in summer (Daugherty, 1952). Simmons (1957) found that the number of species in the Laguna Madre was lower in summer than in winter. Simmons also reported that the numbers of C. sapidus found in the Laguna increased in winter when salinity was low, but this was not true in December, 1956, when salinity was high. The following observa­tions by the writer indicate that C. sapidus differs from the Crustacea listed by Kinne and Rotthauwe (1952) wlth regard to salinity tolerance at high temperature: l. Occurrence of C. sapidus in Aransas Bay during the spring and summer of 1956 followed the pattern reported by Daugherty (1952). They were abundant there in May when salinity was about 32 %o, but only C. danae was captured there in July when sa­linity was about 38 %o-Large male C. sapidus were captured in the headwaters of St. Joseph's Bay and in the Guadalupe River which drains into it, in July, August, and September. Salinity in the river at the time and place of capture was about 20 %o­ 2. C. sapidus were plentiful in the Laguna Madre in February, 1956, ata salinity of 38 %o and a temperature of 22ºC. 3. They were also plentiful there in August at S = 58 %o and T = 33°C. 4. They were scarce there in December at S = 48-58 %o and T = 20ºC, although crabs eaptured then were hypo-regulating. 5. Crabs from Austwell, aeclimatized to normal sea water and subjected to hyper­saline stress showed sorne regulatory ability and great salinity tolerance. 6. Crabs captured in the Laguna in December and treated as in "5" died rapidly, and did not regulate as well as crabs in "5." While seasonal variations in distribution might well be due to factors other than de­creased regulatory ability, points 3 and 5 indicate that high temperature does not impair ability to withstand high salinity. Although C. sapidus from the Laguna differed in response to hypersaline stress from open hay and river crabs, the evidence for genotypic physiological differences is not extensive. Responses to osmotic stress varied, but representatives of the two populations always behaved as separate groups. lt was shown by Odum (1953) that C. sapidus from Florida rivers could survive transfer from normal sea water to very dilute water if an intermediate salinity stage was used. This was found true for river crabs in Texas, but not for Laguna crabs, although periods of acclimation to normal sea water were not equal. In two out of three tests, Laguna crabs withstood high salinity better than river crabs after both groups had been acclimated to 1007c S.W. Comparison of Vea and Oeypode with Callineetes reveals both similarities and differ­ences. Both groups can withstand salinities up to twice normal sea water, but the land crabs regula te blood concentrations of ali ions and ( probably as a consequence) os­motic concentration, within relatively narrow limits, while blue crabs tolerate a greater rise in total blood concentration and regulate mainly magnesium and sulphate. Abso­ lute concentrations of magnesium were lower in the blood of Ocypode than in Cal­linectes, while blood sulphate concentrations were just the opposite (i.e., lower in Callinectes). Land crabs show a decrease in urinary' sodium concentration, either in response to salinity or temperature stress; this response was not found in blue crabs. In both land crabs and blue crabs, the antennary gland appears to function in the regu· lation of magnesium and sulphate. Land crabs ( except possibly Pachygrapsus) also seem to regulate potassium by way of the mine, while in Callinectes both blood and urine potassium are high. The higher total blood concentration of Callinectes, under hyper­saline stress, compared to Ocypode, is probably due to difference in sodium and chloride regulation; both of these substances are well-regulated in Ocypode. Evidence implicating the gut in water absorption and salt excretion (in both types of crabs) is worthy of verification and further testing. If the conclusions of Potts (1954) concerning the energetics of hyper·regulation can be reversed, the most efficient means of meeting hy'per-osmotic stress would be to allow a slight rise in blood concentration. Both types of crabs use this mechanism to sorne extent, but it is most pronounced in Callinectes, where stress is continuous. Increased stress would require water conservation and salt excretion against a gradient. Produc­tion of a hypertonic urine would accomplish this, but evidence for its occurrence is not impressive. Prosser et al. (1955) did not find hypertonic urine in Pachygrapsus. In Uca and Ocypode slight urine hypertonicites were found, both in this investigation and in that of Green et al. (1959), but the cessation of urine production in air makes this observation of doubtful value. In blue crabs, during the first two days of high salinity stress, U / B and stomach fluid to blood ratios reached 1.2, but declined to under 1.05 by seven or eight days, as blood concentration rose. It may be that slight urine and stomach fluid hy'pertonicities, comhined with a large flux of water through the animal, play sorne part in hypo-regulation. Another factor which may' affect hypo-regulation in both land and blue crabs is the permeability of the body surface. Potts (1954) stressed its importance. An inverse relationship between permeability and regulatory ability in crabs has been reported by Gross (1957), who suggested that regulating mechanisms might be present in poor or non·regulators, but the mechanisms might be cancelled out by high permeabilities. Permeabilities of the body surface of Callinectes and Ocypode should be measured and compared. Hypo-regulatory ability' of land crabs decreases at high temperatures, while in blue crabs from the Laguna Madre it either increases or is insensitive to temperature. While severa} workers have reported changes in blood concentrations of euryhaline forms be· tween winter and summer, actual tests of the effect of temperature on regulatory ability are not numerous. It was shown in the present investigation that Uca pugnax from Woods Hole regulated blood better (in 190% S.W.) at 21° than at 10 or 30ºC. It would be interesting to compare northern and southern populations of Uca in this manner ( using smaller temperature increments) to see if the temperatures of maximal regula· tion differed. The same thing should be done with Callinectes. lndividuals of this species from the Laguna Madre differed from individuals from a neighboring brackish water population with regard to salinity-temperature tolerance, and may differ even more from northern populations. In any case, it is evident that salinity and temperature tolerance are interdependent, and cannot be considered separately. Osmotic and lonic Regulation in the Blue Cmb and the Ghost Crab Summary l. Blood of urine concentrations of Na, K, Ca, Mg, Cl, and S04 are given for Ocypode albicans in external concentrations from 14 to 197% S.W. All ions are regulated to sorne extent in ali salinities at temperatures between 12 and 25ºC., but regulatory· ability is reduced at temperatures of 29-35°C. 2. Temperature has a pronounced effect on hypo·regulatory ability of both Ocypode and Uca. Neither species can survive comhined high temperature and high salinity; Uca regulates blood better (in 190% S.W.) at 21 ° than at 10 or 30º C. 3. Decreased urine Na concentrations occur in Uca pugnax, Ocypode albicans, and Cardisoma guanhumi when subjected to hyper-saline stress. In Ocypode, the effect is most pronounced at high temperature. 4. In Uca and Ocypode, injection of MgCl2 alters urine Na concentration. The latter increases if initially low, decreases if initially high. 5. Callinectes sapidus has limited hy'po-regulatory ability for total blood concentration and marked ability to regulate blood magnesium and sulphate, hoth in a high salinity lagoon and in the laborátory. 6. C. sapidus from the high salinity lagoon are more tolerant of high salinity and less tolerant of low salinity than are crabs from a brackish river, at least in summer, but evidence for a genotypic difference is not conclusive. 7. C. sapidus from the Laguna Madre seem to withstand combined high temperature and high salinity better than other crabs mentioned in the literature. 8. Sorne evidence implicating the gut in osmotic and ionic regulation ( especially of magnesium and sulphate) is presented for both C. sapidus and Ocypode albicans. Acknowledgments 1 wish to thank the director and staff of the lnstitute of Marine Science and Mr. Ernest Simmons of the Texas Game and Fish Commission for their hospitality and for their assistance in the performance of this work. 1 also wish to thank Dr. C. L. Prosser for guidance while the work was in progress, and Drs. Prosser, Wm. McFarland, and H. T. Odum for reading and correcting the manuscript. A pre·d?ctoral stipend was fur­nished by The University of Texas. Literature Cited Barnes, H. 1954. Sorne tables for the ionic composition of sea water. J. Exp. Biol. 3'1: 582-584. Baumberger, J., and J. Olmstead. 1928. Changes in osmotic pressure and water content of crabs during molt cycle. Physiol. Zoo!. l: 5.31-5144. Beadle, L. C. 1957. Comparative physiology: osmotic and ionic regulation in aquatic animals. Ann. Rev. Physiol. '19 : 329-358. Broekema, M. M. M. 1941. Seasonal movements and the osmotic behavior of the shrimp, Crangon crangon L. Archiv. Neerl. Zoo!. 6(1): 1-100. Collier, A., and J. W. Hedgpeth. 1950. An introduction to the hydrography of tidal waters. Pub!. lnst. Mar. Sci. Univ. Tex.1(2): 121-194. Conklin, R. E., and A. Z. Krogh. 1938. A note on the osmotic behavior of Eriocheir in concentrated, and Mytilus in dilute, sea water. Ztschr. vergl. Physiol. 26 : 239-248. Daugherty, F. M. 1952. The blue crab investigation. Tex. J. Sci. IV : 77--{!4. Edmonds, E. 1935. The relations between the interna! fluid of marine invertebrates and the water environment, with special reference to the Australian Crustacea. Proc. Linn. Soc. New So. Wales 60: 23~247. Flemister, L., and S. Flemister. 1951. Chloride ion regulation and oxygen consumption in the crab Ocypode albicans (Bosq.) Biol. Bull. Woods Hole 101: 259-273. Flemister, L. J. 1958. Salt and water anatomy, constancy and regulation in related crabs from marine and terrestrial habitats. Biol. Bu!!. Woods Hole 115: 180-200. Flemister, S. C. 1959. Histophysiology of gill and kidney of crab Ocypode albicans. Biol. Bull. Woods Hole 116: 37-48. Gifford, Charles A. 1958. Sorne aspects of osmotic and ionic regulation in the blue crab, Callinecets sapidus, and the ghost crab, Ocypode albicans. Ph.D. Thesis, Univ. of Illinois. Green, J. W., M. Harsch, L Barr, and C. L. Prosser. 1956. (Abstract) Ionic regulation in the fiddler crabs, U ca pugnax and Uca pugilator. Biol. Bull. Wood's 'Hole 11'1: 290. Green, J. W., M. Harsch, L. Barr, and C. L. Prosser. 1959. The regulation of water and salt by the fiddler crahs UCa pugnax and Uca pugilator. Biol. Bull. Woods Hole 116: 7fH37. Cross, W. J. 1954. Osmotic responses in the sipunculid Dendrostromum zostericolum. J. Exp. Biol. 31: 402-423. ----. 1955. Aspects of osmotic regulations in crabs showing terrestrial habitat. Amer. Naturalist LXXXIX (847): 205-222. ----. 1957. An analysis of response to osmotic stress in selected decapod Crustacea. Biol. Bull. Woods Hole 112: 43-62. ----. '1959. The effect of osmotic stress on the ionic exchange of a shore crab. Biol. Bull. Woods Hole 116: 248-257. Gunter, G. 1950. Seasonal population changes and distributions as related to salinity, of certain invertebrates of the Texas Coast, including the commercial shrimp. Pub!. Inst. Mar. Sci. Univ. Tex. I (2) : 7-51. Hedgpeth, J. W. 1947. The Laguna Madre of Texas. Trans. 12th N. Amer. Wild Life Conf., 364-380. ----. 1953. Zoogeography of the Gulf of Mexico. Pub!. Inst. Mar. 'Sci. Univ. Tex. 3(1): 107-224. Jones, L. L. 1941. Osmotic regulation in severa! crabs of the Pacific Coast of North America. J. Cell. and Comp. Physiol. 18: 79-9'2. Kinne, O., and H. W. Rotthauwe. 1952. Biologische Beobachtung und Untesuchungen uber die Blutkonzentration an Heteropenope tridentalis Maitland (Dekapoda). Kieler Meeresforsch. 8: 212...:211. Ladd, H. S. 1951. Brackish water and marine assemblages of the Texas Coast, with special reference to molluscs. Pub!. Inst. Mar. Sci. Univ. Tex. 2(1): 1'25-163. Nalefski, L. A., and F. H. Takano. 1959. A photonephelometric method for the determination of sulfates in biologic fluids. J. Lab. Clin. Med. 36: 148-470. Needham, A. E. '1957. Factors influencing nitrogen excretion in Crustacea. Physiol. Comparata el Oecol. 4: 209...:z39_ Newcombe, C. L., and E. H. Gray. 1941. Observations on conservation of the Chesapeake Bay blue crab, Callinectes sapidus (Rathbun). Va. J. Sci. 2: l. Nicol, J. A. C. 1960. Water, salts and minerals, p. '28-83. In The biology of marine animals. Sir Isaac Pitman & Sons, Ltd., London. 707 p. Odum, H. T. '1953. Factors controlling marine invasion into Florida fresh waters. Bull. Mar. Sci. Gulf Carib. 3: 134-156. Panikkar, N. K. 1941. Osmoregulation in sorne palaemonid prawns. J. Mar. Biol. Ass. U.K. 25: 317-359. Parry, G. 1954. Ionic regulation in the palaemonid prawn, Palaemon (Leander) serratus. J. Exp. Biol. 31: 601-613. Pearse, A. S. 1932. Freezing points of bloods of certain littoral and estuarine animals. Carnegie Inst. Wash. (Papers from Tortugas Lab.í 8: 93...:102. Potts, W. T. W. 1954. The energetics of osmotic regulation in brackish and fresh-water animals. J. Exp. Biol. 31: 618-630. Prosser, C. L. 1950. Water and inorganic ions, p. 6--H12. In Comparative animal physiology (C. L. Prosser, ed.). W. B. Saunders Co., Philadelphia. 888 p. Prosser, C. L., J. W. Green, and T. J. Chow. 1955. Ionic and osmotic concentrations in blood and urine of Pachygrapsus crassippes acclimated to different salinities. Biol. Bull. Woods Hole 190 : 99-107. Robertson, J. D. 1953. Further studies on ionic regulation in marine invertebrates. J. Exp. Biol. 30 : 277-296. ----. 1957. Osmotic and ionic regulations in aquatic invertebrates, p. 2'29-246. In Recen! advances in invertebrate physiology (B. T. Scheer, ed.), Univ. of Oregon Publications, Eugene, Oregon. 304 p. ----. '1960. Osmotic and ionic regulations; Vol. I, p. 317-3•39. In The Physiology of Crustacea (T. H. Waterman, ed.), Academic Press, New York. 670 p. Schlieper, C. '1956. Physiologie des brachwassers, Band 22, p. 218--348. In Die binnengewasser (Herausgegeben von A. Thienemann ). E. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart, Germany, 348 p. 'Schnor, E. 1934. A study of the cause of death in high intestinal ohstruction: Observations on chlorine, urea and water. Acta Chir. Scand. 75(Suppl. 33): l--'176. Scholander, P. F. '1947. Simple syringe burette. Science 105 (2735): 581-582. Shaw, J. 1955a. Simple procedure for the study of ionic regulation in small animals. J. Exp. Biol. 32: 321-329. ----. 195Sb. lonic regulation in the muscle fibers of Carcinus maenas. II. The effect of reduced blood concentration. J. Exp. Biol. 32: 664--680. Simmons, E. G. 1957. An ecological survey of the upper Laguna Madre of Texas. Publ. lnst. Mar. Sci. Univ. Tex. 4(2): 156-200. Verwey, J. 1958. A plea for the study of temperature influence on osmotic regulation. Union lnternat. des. Sci. Biol. Sér. B, 24: 130-149. Osmotic and lonic Concentrations in the Mantis Shrimp Squilla empusa Say1 BYuNG DoN LEE2 AND W1LLIAM N. McFARLANDª lnstitute of Marine Science The University of Texas Port Aransas, Texas Abstract Osmotic and ionic concentrations of body fluids and muscle in the stomatopod, Squilla empusa, were analyzed as a function of environmental salinity. lndividuals survived gradual changes in salinity ·down to '13 %o as correlated with their distribution with six hours required for isosmotic equilibrium. lndividuals survived rapid salinity changes between 22 to 47%0. With decreasing salinity below 21%0, specimens showed hyperosmotic regulation of serum with sodium, chloride and calcium lending to remain constant. In the muscle, sodium and chloride declined, potassium remained constant, and calcium and magnesium increased. Large differences in composition of fluids were found in recently handled specimens. In normal sea water serum cations and chloride accounted for 95% of the osmotic pressure, but with increased dilution they accounted for only 67% due to the increase of non-protein nitrogenous compounds. lntroduction Osmotic and ionic regulation have been studied extensively· in crustaceans. Severa! important works review this subject (Krogh, 1939; Prosser et aL, 1950; Beadle, 1957; Robertson, 1957, 1960; Schlieper, 1958; and Nicol, 1960). Body fluids of most marine crustaceans are essentially isosmotic with the environment and show little regulation, although ali show at least a limited degree of ionic regulation. Such poikilosmotic and usually stenohaline forros are represented by Maja (Duval, 1925), Hyas (Schlieper, 1929), Portunus (Margaria, 1931; Schwabe, 1933), Lophopan­opeus and Specocarcinus (Jones, 1941) , Cancer antenarius (Jones, 1941; Gross, 1957); Cancer gracilis, Callianassa, Upogebia, Emerita, and Pugettia (Gross, 1957). Forms which show limited osmoregulation tend to invade brackish water. In brackish water their hody fluids are slightly hyperosmotic, but when in sea water usually they maintain isosmoticity. Examples of this type of regulation are represented by Cancer pagurus (Schlieper, 1935), C. magíster, Hemigrapsus, and Rithropanopeus (Jones, 1941) and Asellus (Lockwood, 1959). Similar regulation occurs in Carcinus (Duval 1925; Schlieper, 1929). Hyposmotic regulation of body fluids when in sea water or concentrated salt water occur in Ocypode, Cardisoma, Gecarcinus, and Grapsus (Perse, 1932), Pachygrapsus 1 Data on the effects of changing salinity on Squilla empusa are extracted from a Masters Thesis in Zoology (Marine Science) submitted by the first author to the Graduate Faculty of the Uni­ versity of Texas. Other data are the result of joint effort. 2 Present address: Department of Oceanography and Meteorology, A and M College of Texas, College Station. 3 Present address: Department of Zoology, Cornell University, Ithaca, New York. Osmotú: and lonú: Concentrations in the Mantis Shrimp (Schwabe, 1933b; Jones, 1941), Leptograpsus and Heloecius (Edmonds, 1935), Le­ander and Palaemontes (Panikkar, 1941), Uca (Jones, 1941) and Artemia (Croghan, 1958a). Body fluids of these crustaceans are hyposmotic in normal or concentrated sea water and usually hyperosmotic in brackish water. Severa! papers deal with the effects of rapid and gradual changes in concentration of the medium on the osmotic and ionic concentrations of body fluids of crustaceans. In general, stenohaline forms do not regulate their blood osmotic concentration to either acule or slow changes (Schlieper, 1929; Duval, 1925; Gross, 1957). In contrast, eury­haline forms, including those of terrestrial habitat, have the ability to regulate concen­tration of their body fluids to sudden or slow changes of environmental salinity (Ed­monds, 1935; Prosser, et al., 1955; Gross, 1957; Green, et al., 1959; Croghan, 1958a and b; Lockwood, 1959). For the euryhaline prawn, Palaemonetes varians, Panikkar (1941) found that they could survive in 15 per cent sea water when quickly transferred from normal sea water. Using slow dilution techniques he found Palaemonetes would survive in 0.3 per cent sea water. lonic regulation of severa} marine crustaceans in normal sea water has been studied by Rohertson (1939, 1949 and 1953) . He found that ali ions in the blood varied from their concentrations in the medium. The largest ionic deviations from sea water, and particularly the lowest magnesium concentrations, were found in the more active crusta­ceans. Ionic regulation of marine crustacea in varying concentrations of the medium has been investigated by severa} workers. In the prawn, Palaemon, potassium, calcium, magnesium and sulphate are relatively constant but sodium and chloride decrease with environmental dilutions to 50 per cent sea water. At this dilution they are slightly higher than the environmental concentrations of sodium and chloride. lnstances of active ionic accumulation have been demonstrated among the following species in dilute media: Eriocheir (Krogh, 1938; Koch, 1954; Koch, et al., 1954), Carcinus (Webb, 1940) , Artemia (Croghan, 1958 a and b) and Asellus (Lockwood, 1959). Muscle ionic and osmotic regulation of marine crustacea have not been studied ex­tensively. Shaw (1955 a and b, 1958 a and b) found that the muscle fibers of Carcinus are probably always in osmotic equilibrium with the blood. Apparently calcium and magnesium ions are passively' distributed, whereas sodium ions are actively pumped from the cell and potassium ions are accumulated. Robertson (1957) indicates that cellular potassium does not stand in Donnan equilibrium with extracellular potassium in crustacea except for Carcinus. In spite of the many studies that have been performed on aquatic crustacea, osmotic and ionic regulation in various sea water concentrations for the stomatopod mantis shrimps have not been investigated. lonic regulation of Squilla mantis has been studied in normal sea water (Robertson, 1953). He found Squilla to have a similar typ~ of ionic regulátion as in severa} purely marine decapods, i.e., accumulation of cations except for magnesium. This investigation reports osmotic behavior of the mantis shrimp Squilla empusa and also ionic changes in body fluids and muscle as a function of salinity of the externa} medium. Squüla empusa commonly inhabits coastal seas and the bottoms of shallow muddy bays where the salinity is to a varying degree affected by fresh water drainage. Osmotic and lonic Concentratwns in the Mantis Shrimp Materials and Methods CoLLECTION AND CARE oF ANIMALS Squilla empusa were collected from Corpus Christi Bay, Aransas Pass Channel and the Gulf of Mexico, Texas, with a 25 foot otter trawl. Twenty minute hauls were made each time. The collected animals if not immediately sampled were kept on board in running sea water until transferred to the laboratory. When not used experimentally, the animals were fed pieces of fresh fish or shrimp once a day. Food residues were re­moved as soon as possible to avoid contamination. Water in the holding tank was re­filled daily with incoming tidal water from the Aransas Pass Channel. Salinity of this water fluctuated between 29 and 31 parts per thousand (%0 ). Special care was taken to refilter water in all experimental tanks. ANALYTICAL METHODS Blood samples were collected with a glass cannula inserted into the ventral venous sinus. Blood was gently sucked from the sinus and discharged below the surface of ion­free paraffin oil in 15 mi centrifuge tubes. After collection, blood samples were placed on ice until analyses were started, usually within two hours. The blood samples were centrifuged and the clear blue serum pipetted off for chemical analyses. Muscle samples, of approximately one gram wet weight for chloride determinations and 200 mg wet weight for flame analysis, were excised from the abdominal region of the dorsal muscle mass of each animal. After weighing, drying and reweighing, samples were mashed in a beaker and then digested in 0.2 mi of nitric acid and 2 ml of superoxol following the technique of Gordon (1959). The digested samples were filtered and diluted to 10 ml. Serum freezing point depressions were determined with a Fiske Osmometer using 0.2 mi samples. Results are reported as milliosmols (mO) and/ or as degrees centigrade depression. The method of Schales and Schales ( 1941) was used for all chloride determinations. Water samples were titrated directly, but serum samples were digested with 0.2 mi of concentrated nitric acid and 2 ml of superoxol. The digested samples were diluted to 10 mi and centrifuged to remove fragments. A 2 ml portion of the diluted sample was used for titration. Sodium and potassium were measured with a Beckman DU flame photometer by the direct method at 590 and 770 millimicrons. Calcium and magnesium were analyzed also with a direct method at 422. 7 and 371 millimicrons, following the technique of Prosser, et al., (1955). Due to interference efforts and low emission for these bivalent cations the error in their analysis might be appreciable. Serum protein was estimated by the method of Robinson and Hogden (1941) using 3 ml samples of serum. Trimethylamine oxide content of serum was determined by the method of Dyer (1945) with 0.2 ml samples, while total non-protein nitrogen was ob­tained for 0.5 mi samples by standard micro-Kjeldahl technique. EXPERIMENTAL METHODS Blood samples were collected immediately after recovery of mantis shrimp from the trawl. At the same time, the bottom water was collected for chemical analysis with a Kemmerer water sampler. Several animals were transferred into a holding tank for two days before sampling to determine if any differences occurred in the body fluids due to handling and confine­ment. In several experiments mantis shrimp were subjected to rapid salinity changes both above and helow normal salinities (29-31 %o). In these experiments distilled water was used to dilute sea water, while sea water was boiled to increase salinity. Changes in sea water concentration, whether diluted or concentrated, were made volumetrically. Speci­mens were transferred into severa] different concentrations and sampled at progressive intervals to determine how rapidly they adjusted the concentration of their body fluids. In other experiments mantis shrimp were subjected to more gradual salinity changes. In these experiments the medium was diluted every 24 hours with water of salinity 2 %o from a natural pond. Body fluids from three specimens and muscle from one specimen were analyzed after 24 hours at each concentration. Osmotic and lonic Concentration of Serum and lonic Concentration of Muscle of Squilla empusa at Environmental Salinities SERUM ÜSMOTIC CONCENTRATION Osmotic concentrations of serum of Squilla empusa, as measured by freezing point depression, were found to he isosmotic or slightly hyperosmotic to the surrounding sea water (black circles, Fig. 1). However, serum was slightly hyposmotic with respect to the environment (triangles, Fig. 1) when specimens were held in the laboratory for one or two days. The data indicate that trawling induced a slight hyperosmoticity in the lle LO l.> 2.0 l600 1 2-0 lli ! 2 ,. 1.0 0:5 2001ú.._•oo'--~~~-~ o1000 1200:-::--'-~~ .oo_.__.._~~:-::--'-~,~.oo='= GONCE TRATION OF MEDIUM (Milliosmols) Fu;. l. Relationship of bo e:: w 800 (f) lL. o 600 z r "" ;i 400 r z w ~ o u 200 400 soo eco 1000 1200 CONCEN TRATION OF MEOIUM(Miliosmols) F1c. 2. Relationship of body fluid osmotic con­centration to environmental osmotic concentra­tions for Squilla empusa when subjected to slow dilution. Each group of data represents the osmotic con­centration of fluids after 24 hours exposure to the respective salinity. Ali specimens were sub· jected to progressive dilution every 24 hours. body fluids. Statistical comparison reveals that the mean milliosmolal concentration for each group is significantly different [P (jtj > 3.355) = 0.005, where t = 14.05]. Similar results have been obtained for isosmotic vertebrales after handling (McFar­land and Munz, 1958). However, attempts to induce hyperosmoticity through artificial handling of mantis shrimp, previously held in the laboratory, produced variable results. Sorne specimens were hyperosmotic, whereas others were isosmotic or hyposmotic. SERUM loNrc CoNCENTRATION The concentration of sodium, potassium, calcium, magnesium and chloride in the serum of S. empusa immediately after capture and after being held for two d~ys in the TABLE 1 Concentration of ions in blood serum of Squilla empusa from trawl collections and after holding in the laboratory for 48 hours• Ion concentration expressed as mEq/liter Sample Millio1mols Na• K• Ca++ Mg++ a· Sum or ioa1 Trawl Collection, sampled immediately 'Serum 1003.6 441.8 15.0 19.2 42.0 430.9 948.9 Sea water 987.0 394.0 9.4 20.0 81.0 502.0 1006.4 Cation to chloride ratio of water 0.784 0.018 0.040 0.16'1 1.000 Holding Experiment, adapted Serum 897.7 348.0 17.0 33.6 52.6 401.7 852.9 Sea water 9'24.6 367.5 10.5 23.0 80.0 451.7 932.7 Cation to chloride ratio of water 0.814 0.023 0.051 0.177 1.000 Oceanic W atert Cation to chloride ratio 0.859 0.018 0.037 0.195 1.000 • Errors of an&;lysis for sodium and potassium were leas than ± 3%; chloride error was +S.5% and can accounl for tbe conslanl low cation lo chloride ratio of trawl collection sea water compared to holding experimenl sea water; mean error for calcium was +5% wbile for magnesium it was ±2.23. Emission error for the latter two elemenls can be bigh and absolute error lhus might be considerable. f Sverdrup et al., 1942. laboratory are shown in Table l. Serum magnesium and chloride were at lower concen­tration than environmental concentrations whether sampled immediately after collection or after holding, whereas sodium was lower in concentration only from specimens held in the laboratory. Potassium approached twice the environmental concentration re­gardless of sampling conditions, whereas calcium was the same in immediately sampled specimens. In the specimens held for 48 hours calcium was 1.45 times as concentrated as in sea water. The sodium, potassium, magnesium, calcium and chloride in the serum, for the speci­mens held for 48 hours before sampling, account for slightly more than 95 per cent of the total osmotic pressure of the body fluids. Since sorne calcium is most probably in bound forro as a calcium-protein complex, the actual total osmotic effect of the ions is certainly somewhat lower than 95 per cent. Presumably the difference is made up by anions, such as sulfate, and by nitrogenous compounds. Unfortunately, no data are avail· able on the. concentration of sulfate while our data on nitrogenous constituents are not sufficient to generalize. As in other crustaceans, sodium and chloride are the most im­portant osmotic constituents, making up 83.5 per cent of the total serum osmotic pressure (749.7 / 897.7 X 100). Examination of the ratio for the various cations to the concentration of chloride for the environmental waters from which the mantis shrimp were obtained and for oceanic water indicates that potassium is normal, sodium and magnesium are low, and calcium is slightly high. The effect of such changes in the ionic constituents of the sea water on ionic balance of S. empusa are difficult to equate. However, in Table 2 the relative ionic levels as a per cent of total cation concentration are compared with several other crus­taceans. Examination of the data for S. empusa when hyperosmotic to the emv.ronment (sampled immediately) and when slightly hyposmotic to the environment (sampled after 48 hours), again indicates that handling seriously affects the ionic concentrations of the serum, as well as the total osmotic pressure. Ali ions are affected but sodium, chloride and calcium are most affected on an absolute basis, while magnesium and po­tassium are changed to a lesser degree. Comparison of data for both hyperosmotic and hyposmotic specimens of S. empusa with other crustaceans reveals that ionically, S. empusa is more like crustaceans that show poor osmotic regulation such as Maja squinado and Hyas araneus (Bethe and Berger, 1931) than crustaceans showing fair to excellent regulation (Table 2). Careful examination of values in this table indicates that the various crustacean species can be classed as forms with ratios either closer to the hyperosmotic specimens of S. empusa or to the hyposmotic specimens. For instance, the values for Maja squinado are more like TABLE 2 Relative ionic concentration of serum in Squilla empusa compared to other crustacea. Numbers in brackets are ratios for sea water. Total Ratio to total cations (based on mEq/liter) catinns Speeies (mEq/ liter) Na+ K+ Ca++ Mg++ a- STOMATOPODA Squilla empusa Hyperosmotic specimens 518.0 0.853(0.781) 0.029(0.019) 0.037(0.04{)) 0.081 (0.'161) 0.832(0.990) Hyposmotic specimens 451.2 0.771(0.764) 0.038(0.022) 0.074(0.048) 0.116(0.166) 0.890(0.950) BRACHYURA Stenohaline Maja squinaáo* 764.1 Hyas araneus• 620.2 Cancer pagurus• 638.4 0.770(0.917) 0.820(0.790) 0.847f0.790) 0.045(0.020) 0.020(0.018) 0.028(0,018) 0.071 (0.010) 0.038(0.034) 0.038(0.034) 0.115(0.053) 0.'120(0.156) 0.085(0:156) 0.812 (0.943) 0.836(0.898) 0.810(0.898) Cancer pagurust 596.7 0.842(0.771) 0.020(0.016) 0.046(0.034) 0.092 (0.179) 0.864( 0.864) Euryhaline Carcinus maenas• 662.4 0.871 (0.790) 0.019(0.018) 0.039(0.034) 0.080(0.156) 0.820(0.888) Pachygrapsus crassipes§ 517.0 0.891 ......... 0.018 .. 0.052 0.039 .......... Homarus americanusll 516.6 0.881 .......... 0.018 . 0.066 0.035 ............ 0.915 .......... Homarus gammarust 576.0 0.898(0.771) 0.025(0.016) 0.052(0.034) 0.025(0.179) 0.924(0.864) Nephrops norvegicus+,* * Palinurus 570.8 0.906(0.771) 0.013(0,016) 0.049 (0.034) 0.032(0.179) 0.908(0.864) elephasll 615.4 0.884 .. 0.017 .. .......... 0.044 ... 0.055 ........... 0.905 • Bethe and Berger, 1931. t Robertson, 1939. ! Robertson, 1949. § Schlaller, 1941. íl Cole, 1940. Hemingsen, 1942. ••Sea water ratios for Nephrops determined by Robertson (1939). the values for hyposmotic S. empusa, whereas values for Cancer pagurus are much mon like hyperosmotic S. empusa. The ionic and freezing point data indicate that resulti depend to a large degree on the previous history of specimens. The inability to con· sistently induce artificial hyperosmoticity in Squilla makes interpretation difficult, sinct the precise osmotic and ionic status of individuals under natural conditions cannot be ascertai11ed from the data. Normal osmotic and ionic concentrations in crustacea need careful investigation. In spite of this uncertainty, it can be said that S. empusa is relatively a poor regulator. Unlike Squilla mantis (Robertson, 1949) it shows relatively high values for magnesium. Since S. empusa is relatively active these results are in contrast with Robertson's corre· lation that reduction in magnesium in marine invertebrates goes hand in hand with rapid movement. However, until replicate analyses of magnesium are made by chemical techniques other than flame photometry, which is subject to interference emissions, the high values reported here must remain quite doubtful. Robertson (1949, 1953) compares the Na+ K/ Ca + Mg ratio for severa! marine invertebrates. He finds values below 4 .. 2 for relatively inactive crustaceans and for other types of invertebrates whether active or inactive. Values from 6.i to 11.5 were found for active crustaceans, like Pachygrapsus and S. mantis. Values of this ratio for S. empusa were 4.2 for hyposmotic specimens and 7.46 for hyperosmotic forms. These differences are primarily the result of large increases in sodium and losses in calcium for the hyper­osmotic forms. MuscLE loNic CoNCENTRATION Analysis of the major cations and chloride ion in muscle of S. empusa, sampled im­mediately after capture and after laboratory adaption for 48 hours, indicate that large changes in the concentration of ionic species occur (Table 3). Sodium, calcium, mag­nesium, and chloride are all less concentrated in adapted animals (hyposmotic serum) than in specimens that are not given time to adapt (hyperosmotic serum}. Only potas· sium is unaffected. Comparison of individual ion concentrations of muscle tissue for non-adapted specimens to adapted specimens suggests that when animals are roughly handled sodium, calcium, magnesium and chloride rapidly invade the extracellular muscle-tissue spaces. The ratios of values sampled immediately to values obtained after TABLE 3 Relative ionic concentration of muscle in Squilla empusa compared to other crustacea Concentration of ion in mEq/kg water. Mean SE (number samples) Species Na+ K+ Ca++ Mg++ c1­ Squilla empusa Sampled immediately• 163.5±12.8(7) 87.4±7.0(7) 16.9±3.1 (7) 4'25±3.0(7) 176.7±'13.5(7) Sampled after adaptationt 87.4±18.9(4) 89.9±6.0(4) 7.1±1.3(4) 29.6±4:1(4) 109.3± 6.3(4) Nephrops norvegicust 83.2 166.6 10.4 38.2 109.9 Carcinus maenas§ 54.0 146.0 10.0 34.0 53.0 * Sampled after capture. 33%o sea water. t Adapted 48 hours in laboralory al 32%0 sea water. l Roberlson, 1957. § Shaw, 1958b. Osnwtü: and lonic Concentratwns in the Mantis Shrimp 48 hours in Table 3 are: Na= 1.87; K = 0.975; Ca= 2.38; Mg = 1.44; and Cl = 1.62. Only the ratio for potassium remains close to unity while the ratios for sodium, mag­ nesium and chloride are high but similar. With the exception of potassium the concentration of muscle tissue ions for the speci­mens held for 48 hours agrees favorably with the few published results for other crus· taceans (Table 3). Characteristically, potassium is concentrated in the muscle tissue and is approximately 5.5 times higher than in serum. The apparent stability of potassium in the muscle tissue between roughly handled and adapted animals does not negate its pos­sible movement into the extracellular spaces. Movement of potassium into the extracellu­lar muscle-tissue spaces could remain undetected due to the large amounts of the ion present in the tissue as compared to the serum. Osmotic Changes in Squilla empusa When Exposed to Different Concentrations of Sea Water EFFECT OF R.APID IMMERSION IN DILUTE SEA wATER Specimens previously held for 48 hours in sea water with an osmotic concentration of 907 mO were abruptly transferred in groups of 10 to tanks containing varous dilutions of sea water. Considering the water with a concentration of 907 mO as 100% sea water, the concentrations of various tanks were: 92.5% (837 mO); 75% (682 mO); 52.5% (476m0); 27% (246m0); and 12.5% (112m0). Watertemperatureduringthe24 hour period of experimentation varied from 18.0° to 20.5ºC. Behavioral responses of the specimens when placed directly into the various salinities were as follows: 100% sea water. Specimens were normal throughout the experimental period showing no signs of stress or unusual activity, such as loss of equilibrium. 95% sea water. No differences were noted from animals in 100% sea water. 75% sea water. lmmediately after introduction a marked reduction in motility was noted, but equilibrium was not lost. Severa! of the specimens attempted to propel them­ selves from the water. After one hour, however, normal movements were observed. Further behavioral deviations were not observed for the remaining 23 hours of the experiment. 52.5% sea water. Five of the ten specimens in this group immediately sank upside down to the bottom and lay motionless except for slow movements of the swimmerets. The other specimens did not show upsets in equilibrium but were much less active than controls. One hour after introduction one specimen was dead, while by six hours six animals were sampled and the remaining four shrimp were dead. 27% sea water. Ali specimens responded by turning upside clown on the bottom. All were moribund, only the swimmerets showing motion. After one hour ali animals but one were dead. 12.5% sea water. All animals responded as in 27',k sea water. After 30 minutes nine were dead and at 50 minutes the remaining shrimp ceased ali movements. Dilutions of sea water greater than 75% are rapidly lethal to S. empusa under con­ ditions of immediate transfer from normal sea water. Osmotic concentrations of serum removed from specimens at progressive times during the experiment for 100, 92.5, 75 and 52.5% sea water revea! that serum becomes-isosmotic to diluted sea water after approximately six hours exposure. EFFECT OF RAPID IMMERSJON IN Co~cENTRATED SEA WATER A separate but otherwise similar experiment to the acule dilution experiment was performed for concentrations of sea water greater than 100%. As in the dilute experi­ments isosmotic adjustment of the -body fluids occurred within six hours. Behavioral reponses of these groups to increased salinity were: 100% sea water. As before, this group served as a control and showed normal move­ments and equilibrium throughout lhe experiment which was extended to 60 hours. 109% sea water. This group showed no noticeable changes in behavior. 149% sea water. No noticeable change was observed in the behavior of this group throughout the entire 60 hours except that one animal died after seven hours exposure. 168% sea water. After 30 minutes exposure two specimens were upside clown and immobile. The remainder showed a reduction in motility. At one hour ali specimens were upside clown and showed only slight movements of the swimmerets. At six hours ali specimens were moribund. This group was discontinued after six hours exposure. 200% sea water. lmmediately after immersion all animals in this group lost equi­librium, lay upside clown on the tank bottom, and showed only slow movements of the swimmerets. After one hour ali motion ceased and the group was removed. The results of dilution and concentration experiments show that S. empusa has no ability to osmoregulate its body fluids rapidly. Under acute conditions when previously adapted to salinities of approximately 31 %o (907 to 934 mO), the maximum salinity tol­erance range varied from 22 %o to 46.5 %0• Within this salinity range, S. empusa shows less behavioral deviations in response to increased salinity than to decreased salinity. EFFECT OF SLOW CHANGES IN SALINITY To test the possibility that S. empusa might survive at concentrations below 22 %o, a series of groups, each containing three individuals, were placed in lower and lower salinities each day. Samples of serum were analyzed for one group at each salinity' after 24 hours exposure. In contrast to results for rapid dilution (Fig. 1), isosmoticity of the serum at ali concentrations does not occur (Fig. 2). Rather, at 78% sea water (con­sidering the highest concentration for this experiment of 909 mO as 100% sea water) the serum of S. empusa becomes slightly hyperosmotic to the environment and at 39% sea water (335 mO) is about 41 % more concentrated. At lower concentrations, the ani· mals deviate from normal behavior and become moribund (Fig. 2). These results indicate that S. empusa is osmotically' a typical stenohaline crustacean and shows, at best, only a slight degree of osmotic regulation. lt compares closely with Cancer pagurus (Duval, 1925). lonic Changes in Body Fluids Following Changes in Concentration of the Medium Sodium, potassium, calcium, magnesium and chloride concentrations in serum, de­crease with environmental concentrations. In Figures 3, 4, 5, 6 and 7 are plotted the .--~~~--~~~~~-----­ 100~---------------~ 600 () ~ '> 500 ·3 () il" .Loo :::; "'15 o 300 A • ()• A (/) C> o o o 200 _J C> () p @ () 100 O"--~-~~~~-~-~--~-~ o 100 200 300 400 500 600 700 SEA WATER SODIUM (m-equiv./1.) F1c. 3. Relation between serum sodium con­centration and sea water sodium concentration. Black circles are data for specimens sampled immediately after capture; triangles data for specimens held for 48 hours in the laboratory; and semi-open faced circles values for specimens subjected to slow dilution. The diagonal line through the origin represents equal concentration in serum and medium. 600 ' A ·~ 500 C" " i400 w e• A 'ff; ~ ' o a: 300 o _J E ~ C>A e• I C> L) 200 () () o o ~ 100 ºE E () Ü) 60 A z 50 <.? w Cl ~•o o 30 o • o 20 ..J ID 10 01<.o-.i......_._...........................................~.................. ~........~~~ o 8 16 24 32 40 48 56 64 72 80 88 96 I04 SEA WATER MAGNESIUM (m-equi\t/\l F1c. 7. Relation between serum magnesium concentration and sea water magnesium concen­tration. The symbols are the same as in Figure '3. The straight line through the origin shows equal concentration in serum and medium. o 250 => ';l o ·:; o g-200 i • ~o w o ¡;:: 150 •• o o ..J :I: o ti • u o w 100 tº o.:. ..J dJ o u (/) ::::> Cl.f 6 o :i: 50 Cl Cl ¡ Cl BLOOD CHLOR\DE (m-equiv./\.) F1c. 8. Relation between muscle chloride con­centration and serum chloride concentration. Black circles represent data for specimens sampled immediately after capture; triangles data for specimens held for 48 hours in the lab­oratory; open faced circles result from specimens subjected to quick dilution in salinity ; and semi­open faced circles values for specimens subjected to slow dilution in salinity. correlated with the hyperosmoticity found in body fluids in the slow dilution experiments at environmental concentrations below 600 mO (Figure 2). The osmotic effects of the various ions at different concentrations of sea water are indicated in Table 4. lnterestingly, the relative concentrations of total cations and chlo­ride, and of sodium and chloride to total serum osmotic pressure become less with de­creasing environmental salinity. Below 60% sea water ionic contribution is essentially constant at 66-69% of the serum concentration. This is in contrast to the values of 95% found for animals held and handled carefully for several days before sampling. The dif­ferences certainly must be caused in part by unmeasured anions and by nitrogenous compounds. In a separate experiment, S. empusa were subjected to slow dilution overa period of one week until the final sea water concentration was 50% of the initial concentration. In addition to freezing point and ionic analysis, the protein, non-protein nitrogen, and trimethylamine oxide concentrations of serum were determined (Table 5). The final TABLE 4 Per cent contribution of cations and chloride to serum osmotic pressure. Specimens were held for 24 hours at each concentration and sampled. Per cenl Osmotic concenlration Per cent total cations Per cent sodium sea water of serum (mO) and chloride and chloride 100 931 104.0 95.0 95 900 102.0 93.3 89 857 93.8 86.0 85 786 77.8 68.8 78 701 77.0 71.5 60 620 66.5 60¡1) 51 528 69.5 63.0 39 502 67.4 60.0 TABLE 5 Distribution of serum constituents of Squilla empusa subjected to slow dilution of environmental salinity. lnitial concentration of sea water was 32%0 (930 mO) . Final concentration of sea water was 50 per cent. Ali values but K+ and Trimethylamine (TMAO) are rounded to the nearest whole number. Total mEq/liler Pt-r cent Sample conc. total cations Protein TMAO NPN mO Na+ K+ Ca++ Mg++ c1-and c1-g/liter mg/liter mg/100 mi 1 545 211'2 5.6 14 22 209 83 25 0.75 50 2 570 225 5.6 14 26 202 83 23 0.74 36 3 523 187 6.6 15 22 202 83 20 1.55 43 Mean 546 207 5.9 14 23 204 83 23 1.01 43 Sea water 463 180 4.9 8 39 255 94 serum osmotic pressure was similar to previous experiments, but contributions of cations and chloride were higher (83% as opposed to 70%) . Concentrations of protein in serum were quite low and only one-third of the value of 65 g/ liter of plasma reported by Robertson (1960) for Squilla manlis. Trimethylamine oxide was exceedingly low and therefore contributed little if any osmotic effect. In contrast, the non-protein nitrogen fraction was very high and exceeded every value reported by Florkin (1960) for a variety of crustaceans. However, even if these high concentrations of nitrogen were present as amino acids like alanine, glycine or glutamic acid they would not account for the osmotic difference of 92 mO between total concentration of serum and ionic species (546 minus 454, Table 5). Whether these ionic contributions to total serum osmotic pressure would have returned to normal (near 95%) for test periods in excess of 24 hours is unknown. The values of 104 and 102% reported for 100 and 95% sea water (Table 4) possibly are high because of the inclusion of protein-bound calcium in values for summed cations. lonic Changes in Muscle Tissue F ollowing Changes in Concentration of the Medium Concentration of sodium, potassium, calcium, magnesium and chloride were de­termined for muscle tissues of S. empusa both under natural conditions and experimental conditions. Data found for muscle ions in normal sea water concentrations were re­ported and compared with other crustaceans in Table 3. Muscle concentrations of chloride and potassium ions in mEq/l are plotted against their respective serum concentrations in Fig. 8 ( chloride) and 9 (potassium). Multipli­cation of individual muscle concentrations by 1.21 expresses the concentration in mEq/kg water (factor based on overall average water content of muscle). A definite relationship exists between muscle and serum ionic concentrations for sodium and chloride ions. Both the sodium and chloride in muscle decrease with serum concentration. This tendency is less, however, where the animals have been subjected to sudden changes in salinity. Since both serum sodium and chloride tend to decrease with decreases in environmental concentrations (Fig. 3 and 4) the declines in muscle sodium and chloride indirectly reflect environmental changes in these ions. The high correlation between muscle sodium and chloride (Fig. 10) indicates that they move jointly into and out of muscle tissue. Where deviations do occur they" are 250 ~ ~ ·5 cr 4) 200 i w o oc 150 o _J :e u w 100 _J u U) :::> ::!! 50 o • o • o ••• ••• o • C> ºº • o "' • "º ºº o o C> Q) C> C> 0 0~~~5~0~~~10~0~~1~50~~~~250......._. 200~~~ MUSCLE SODIUM (m-equiv./I.) F1c;. 9. Relation between muscle potassium F1c;. 10. Relation between muscle chloride concentration and serum potassium concentra­concentration and muscle sodium concentration. tion. Symbols are the same as in Figure 8. Symbols are the same as in Figure 8. correlated with acute changes in salinity, rather than with slow changes. These results are in keeping with the concept that muscle chloride and sodium are found primarily in the extracellular muscle spaces (Hayes and Pelluet, 1947; Steinbach, 1940; Conway, 1954; GordQn, 1959). Muscle potassium, in contrast to sodium and chloride, remains relatively constant regardless of the serum potassium concentration (Fig. 9). Since serum potassium also declines with environmental potassium (Fig. 5), the constancy of muscle potassium supports the concept that it is primarily intracellular (Hayes and Pelluet, 1947; Gross, 1958) . Shaw ( l 955b) , in contrast to the constancy of muscle potassium found here for Squilla empusa, reports that in Carcinus maenas muscle potassium decreases from 150 mM/ kg muscle water to 80 mM/kg muscle water as blood potassium declines from about 14 mM/ liter to 8mM/ liter. Below serum levels of 8mM/liter, muscle potassium was constant at 80 mM/kg muscle water. lt is quite possible that muscle potassium values for S. empusa would change given more than 24 hours to regulate. However, exposure of animals to slow changes of external salinities for periods up to 11 days did not effect changes in muscle potassium concentration. Concentrations Qf muscle calcium and magnesium as a function of serum calcium and magnesium indicate no apparent correlation. However, if the values for rapid dilution experiments, which show high variation, are ignored, a tendency can be detected for both muscle calcium and magnesium to increase slightly as an inverse function of their serum concentration. Changes are sufficiently' slight, particularly for magnesium, to conclude that these concentrations are essentially constant in muscle as a function of changing serum concentration. In his work on Carcinus, Shaw (1955b), found that muscle calcium and magnesium were little affected by dilution of the environment. Discussion The inability of Squilla empusa to regulate body fluids homoiosmotically indicates that this species has long been primarily a marine crustacean. Species that show either fresh water or brackish water tendencies usually are hyperosmotic under such conditions and show isosmoticity only to increased salinity, while euryhaline and terrestrial species show homoiosmotic regulation in either dilute or concentrated media ( Robertson, 1960). Apparently the long residence of S. empusa as a marine crustacean has not necessitated the evolution of more efficient regulatory' devices. Its intrusions into brackish waters are only marginal. Although as yet untested, it is probable that S. empusa achieves the de­gree of ionic regulation it exhibits much like other poikilosmotic crustaceans, namely, by selective secretion of magnesium and possibly sulfate in a urine isosmotic to the blood and environment. Whether this actually occurs must await analysis of the antennal gland excretions. Abundant populations of S. empusa are found along the south Texas coast only in waters near or above 30 %o (Gunter, 1950). Of 92 animals collected by Gunter, during systematic trawl hauls, only six occurred below 30 %o-Three were captured at 16.5 %o, the lowest salinity at which they were encountered. In the Mississippi Delta, Parker (1956) captured S. empusa in relative abundance at salinities down to 25 %o. Our collections in south Texas support these findings. Squilla empusa were encountered pri­marily in the open Gulf of Mexico or in the mouths of primary bays in spring and summer where salinity, when the mantis shrimp were abundant, seldom was less than 25-28%o. The salinities observed with S. empusa in the field agree fairly well with the lower limit of 22 %o established by rapid dilution methods. In contrast, the lower limit of 12­13 %0, established by slow dilution experiments, agrees with the experience of Mr. An­thony lnglis of the U.S. Fish and Wildlife Service. He reports that S. empusa is taken by bait fishermen from Galveston Bay, Texas, at salinities from 11to15 %o. Robertson (1957) indicates that of three crustaceans studied (Erwcheir, Carcinus imd Nephrops) only' in Carcinus did the ratios for potassium and chloride between muscle and serum show their concentrations to be the result of a Donnan equilibrium (Table 6). In this study, ratios of potassium in muscle to potassium in serum approxi· mate ratios of chloride in serum to chloride in muscle, a condition that may indicate a Donnan equilibrium. Values of 3.96 for potassium and 4.32 for chloride were obtained (Table 6). However, values for slow dilution experiments give increasingly high potas­sium ratios, but constant chloride ratios. For instance at 100% sea water the ratios are 8.46 for potassium and 3.29 for chloride, whereas at 39% sea water they are 18.6 and 3.97, respectively. Such widely differing values are difficult to interpret, but S. empusa under normal environmental circumstances could be considered as having muscle ions, like potassium in Donnan equilibrium. TABLE 6 Relative ratios of concentrations of postassium and chloride in muscle to those of blood serum K, ª· Species K; o;-Reference Squilla empusa Hyperosmotic• 4.8 Hyposmotict 3.96 Eriocheir sinensis 18.4 Carcinus maenas 8.8 Nephrops norvegicus 20.6 -....-, •w• .,.. .. · -· ·­ 3.0 4.32 3.21 Robertson, '1957 10.5 Robertson, 1957 9.39 Robertson, 1957 • Vnluea from animal&sampled in the natural environment. t Values from nnimala held in tbe laboralory for 48 hours. Summary ( 1) Osmotic and ionic concentrations of body fiuids and ion concentrations of muscle for the stomatopod, Squilla empusa, are reported as a function of environmental con­centrations. (2) Freezing point depression of body fiuids reveals that S. empusa is poikilosmotic above 23 %o salinity. When subjected to rapid changes in salinity of the environment it survives between 22 to 46.5 %0, but initially shows upsets in equilibrium and behavior. At salinities beyond this range behavioral deviations are not overcome and the animals die. Regardless of the magnitude of salinity stress, about six hours are required for specimens to reach isosmotic equilibrium. When subjected to slow dilution the lower salinity tolerance of S. empusa is extended to 12-13 %0 • At approximately 21-23 %o specimens begin to show hyperosmotic regulation of serum. However, all specimens react slowly below 20 %o­ ( 3) Analysis of serum ions indicates that sodium, potassium, calcium, magnesium and chloride ali tend to decrease in concentration with dilution of the environment. Below 60% sea water sodium and chloride, and to a greater extent calcium, tend to remain constant. This correlates with the noted hyperosmoticity of the serum below 20 %o· ( 4) Sodium and chloride concentrations of muscle both decline with decreases in environmental and serum concentrations. In contrast, potassium remains constant, whereas calcium and magnesium show a slight tendency to increase. (5) Comparison of analysis of body fiuids of S. empusa immediately after collection and after holding for several days shows that considerable differences exist in concen· tration of ions and osmotic pressure. Animals that are not handled carefully are hy­perosmotic to sea water and the concentrations of serum sodium, calcium, and chloride are ali drastically changed. Such differences are sufficient to effect a complete displace· ment in the relative concentration of serum ions. Because of this, ionic balance in Squilla can appear more like that of active homoiosmotic crustaceans than like that of poikil­osmotic crustaceans. lt is concluded that extreme care must be taken in interpretation of reported results unless precise knowledge of how animals were handled is known. (6) The serum cations and chloride account for 95% of the total osmotic pressure for S. empusa at normal sea water concentrations. With increased dilution of the environ· ment they account for much less being only 67% of the total in sea water of 12-13 %o. lt is shown that the balance is made up in part by non-protein nitrogenous compounds, most probably amino acids, but not by trimethylamine oxide or high serum protein concentrations. Acknow ledgments We are indebted to Messrs. Jerry Flumen, Charles Goodwin, and Herman Moore who assisted in the collection of animals. Dr. Austin Phelps and Dr. James Larimer helped in revision of the manuscript. This study was supported by National lnstitutes of Health Research Grant, NIH-6373 (A) , for studies on osmoregulation of organisms inhabiting hypo· and hyper-saline environments. Osmotic arul lonic Concentratwns in the Mantis Shrimp Literature Cited Beadle, L. C. 1957. Comparative physiology: Osmotic and ionic regulation in aquatic animals. Ann. Rev. Physiol. 19: 329-358. Bethe, A., and Berger, E. 1931. Variationen in mineralbestand verschieclner Blutarten. Pflug. Arch. ges. Physiol. 227: 571-584. Cole, W. H. 1940. The composition of fluids and sera of sorne marine animals and of the sea water in whicb they live. J. gen. Pbysiol. 23: 575-584. Conway, E. J. 1954. Sorne aspects of ion transport through membranes. Symp. Soc. exp. Biol. 8: 297-324. Croghan, P. C. 1958a. The osmotic and ionic regulation in Artemia salina (L). J. exp. Biol. 35: 219-233. ----. 1958b. The mecbanism of osmotic regulation in Artemia salina (L.l. J. exp. Biol. 35: 234-242. Duval, M. 1925. Recherches pbysico-chemiques et physiologiques sur le milieu interior des animaux aquatiques. Modifications sous l'influence du milieu exterieu. Ann. Inst. Oceanogr. Monaco 2: 232--407. Dyer, W. J. 1945. Amines in fish muscle. l. Colorimetric determination of trimethylamine as the picrate salL J. Fish Res. Bd. Can. 6(5): 351-358. Edmonds, E. 1935. The relations between the interna) fluids of marine invertebrates and the water of the environment, with special reference to Australian Crustacea. Proc. Linn. Soc. N.S.W. 60: 233-247. Florkin, M. 1960. Blood chemistry, p. 141...!159. In T. H. Waterman, (ed.), The physiology of crustacea, Academic Press, New York. 6i0 p. Gordon, M.S. 1959. lonic regulation in the brown trout (Salmo trutta L.) J. Exp. Biol. 36: 2'27-252. Green, J. W., M. Harsh, L. Barr, and C. L. Prosser. 1959. The regulation of water and salt by the fiddler crahs, Vea pugnax and Vea pugilator. Biol. Bu!!., Woods Hole 116: 76-87. Gross, W. J. 1957. An analysis of response to osmotic stress in selected decapod crustacea. Biol. Bull. Woods Hole 112: 43-62. ----. 1958. Potassium and sodium regulation in an intertidal crab. Biol. Bull., Wood's Hole 114: 334-337. Gunter, G. 1950. Seasonal population changes and distribution as related to salinity, of certain invertebrates of the Texas Coast, including the commercial shrimp. Pub!. Inst. Mar. Sci. Univ. Tex. 1 (2) : 7-51. Hayes, F. E., and D. Pelluet. 1947. The inorganic constitution of molluscan blood and muscle. J. Mar. Biol. As.s. U. K. 26: 580-589. Hemmingsen, A. M. 1942. Blood sugar regulation in the crayfish. Skand. Arch. Physiol. 46: 51-55. Jones, L. L. 1941. Osmotic regulation in seYeral crabs of the Pacific coast of North America. J. cell. comp. Physiol. '18: 79-92. Koch, H. J. 1954. Cholinesterase and active transport of sodium chloride through the isolated gills of the crab Eriocheir sinensis (M. Edw.). Proc. Symp. Colston Res. Soc. 7: 15-27. Koch, H. J., J. Evans, and E. Schicks. 1954. The active absorption of ions by the isolated gills of the crab Eriocheir sinensis (]\f. Edw.) l\Ieded. y)aasmsche acad. K. Wet. 16: 1-16. Krogh, A. 1938. Active absorption of ions by freshwater animals. Z. vergl. Physiol. 76: 335-350. ----. 1939. Osmotic regulation in aquatic animals. Cambridge Uniwrsity Press, London and New Y orle 242 p. Lee, D. B. 1960. Osmotic and ionic concentrations in the mantis shrimp, Squilla empusa Say. 1\1.A. Thesis, Univ. of Texas. 73 p. Lockwood, A. P. M. 1959. The osmotic and ionic regulation of Asselus aquaticus (L.). J. exp. Biol. 36: 546-555. Margaria, R. 193'1. The osmotic changes in sorne marine animals. Proc. roy. Soc., B. 107: 606-624. McFarland, W. N., and F. W. '.\lunz. 1958. A re-examination of the osmot:c properties of the Paeifie bagfish, Polistotrema stouti. Biol. Bull., Woods Hole 114: 3-IB-356. Nicol, J. A. C. 1960. Water, salts and minerals, p. 28-83. In The biology of marine animals, Sir Isaac Pitman & Sons, London. iOi p. Panikkar, N. K. 1941. Osmoregulation in sorne palaemonid prawns. J. Mar. Biol. Ass. U.K. 35: 317-360. Parker, R. H. 1956. l\facroim·ertebrate assemblages as indicators. Bull. Amer. Ass. Petrol. Geol. 4-0(2): 2%--376. Osrrwtic and Ionic Concentratwns in the Mantis Shrimp Perse, A. S. 1932. Freezing-points of blood of certain littoral and estuarine animals. Pap. Tortugas Lab. 28: 92-102. Prosser, C. L. 1950. Water and inorganic ions, p. 6--102. In C. L. Prosser, (ed.), Comparative animal physiology, W. B. Saunders Co., Philadelphia. 888 p. Prosser, C. L., J. Green, arid T. J. Chow. 1955. Ionic and osmotic concentrations in blood and urine of Pachygrapsus crassipes acclimated to different salinities. Biol. Bull., Woods Hole 109: 99-107. Robertson, J. D. '1939. The inorganic composition of the body fluids of three marine invertebrates. J. exp. Biol. '16: 387-397. ----. 1949. lonic regulation in sorne marine invertebrates. J. exp. Biol. 26: 182-200. ----. 1953. Further studies on ionic regulation in marine invertebrates. J. exp. Biol. 30: 277-296. ----. 1957. Osmotic and ionic regulation in aquatic invertebrates, p. 229-246. In B. T. Scheer, (ed.), Recent advances in invertebrate physiology, Univ. of Oregon Pub!., Eugene, Oregon. 300 p. ----. 1960. Osmotic and ionic regulation, p. 317-339. In T. H. Waterman, (ed.), The physiology of crustacea, Academic Press, New York, 670 p. Robinson, H. W., and C. G. Hogden. 1941. The gravimetric determination of blood serum proteins. J. biol. Chem.140: 85~7. Schales, O., and S. S. Schales. 1941. A simple and accurate method for the determination of chloride in biological fluids. J. Biol. Chem. 140: 879--884. Schlatter, M. J. 1941. Analyses of the blood serum of Cambarus clarkii, Pachygrapsus crassipes and Panulirus interruptus. J. cell. comp. Physiol. '17: 259-26'1. Schliper, C. 1929. Uber die Einwirkung niederer Salzkonzentrationen auf marine Organismen. Z. vergl. Physiol. 9: 478-514. ----. 1935. Neure Ergebnisse und Probleme aus dem Bebiet der Osmoregulation wasser­lebender Tiere. Biol. Rev. 10: 3'34-360. ----. 1958. Physiologie des Brackwassers, Band II, p. 218--348. In Herausgegeben von A. Thienemann, Die Binnengewasser, E. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart, Ger­ many. 348 p. Schwabe, E. 1933a. Uber die Osmoregulation verschiedener Krebse. Z. vergl. Physiol. 19: 183-236. ----. 1933b. Uber die Mineralregulation wasserlebender Evertebratten. Z. vergl. Physiol. 19: 522-524. Shaw, J. 1955a. lonic regulation in the muscle libres of Carcinus maenas. I. The electrolyte compo­sition of single libres. J. exp. Biol. 32: 383-396. ----. 1955b. lonic regulation in the muscle libres of Carcinus maenas. 11. The effect of re­duced blood concentration. J. exp. Biol. 32: 664-680. ----. 1958a. Further studies on ionic regulation in the muscle libres of Carcinus maenas. J. exp. Biol. 35: 902-919. ----. 1958b. Osmoregulation in the muscle fibres of Carcinus maenas. J. exp. Biol. 35: 920--929. Steinbach, H. 1940. The distribution of electrolyes in Phascolosoma muscle. Biol. Bull., Wood's Hole 78: 444-453. Sverdrup, H. U., M. W. Johnson, and R. H. Fleming. 1942. The Oceans. Their physics, chemistry and general biology. Prentice~Hall, New York. 1087 p. Webb, D. A. 1940. Ionic regulation in Carcinus maenas. Proc. roy. Soc. B. 129: 107-136. Phosp:lJ.orus Content of Sorne Fishes and Shrimp in the Gulf of Mexico KENNETH T. MARVIN AND LARENCE M. LANSFORD U. S. Bureau o/ Commercial Fisheries Biological Laborawry Galveston, Texas Abstract The total phosphorus composition was determined for ten species of fish and one species of shrimp found in the coastal and hay waters of Galvest!>n, Texas. The results of the analyses, which were based on the entire animal, were compared with the few similar analyses that have been made on other marine spccies. Shrimp contained about 1.46% P of dry weight (0.35% of wet weight). Fishes contained 2.43 to 3.81 % P of dry weight ( 0.4 7 to 0.84% of wet weight). A brief discussion of the bio­geochemical phosphorus cycle is included. Phosphorus is one of the most measured ingredients of sea water. This element in its ionic form as phosphate is vital to the production of plant life, and most marine scientists, therefore, consider it significant as an indicator of productivity. Phosphorus also occurs in particulate and dissolved organic compounds and in organisms. The importance of this element in food has resulted in chemical investigation of marine products. W. O. Atwater ( 1892) determined the phosphorus composition of many food fish and inverte· brates; later data were summarized by Vinogradov (1953). Most of the work was hased on specific organs, tissues, or parts, rather than the whole animal. This paper presents the phosphorus content of various fishes and shrimp based on the entire animal. The specimens analyzed included inhabitants of the coastal and hay waters of Galveston, Texas, andan undetermined species of lantern fish (family Myctophidae) taken about 50 miles southwest of the Mississippi Delta. These data will be useful in three ways: ( 1) deciding whether chemical composition varíes between species, (2) determining the quantities of phosphorus in the biomass of higher organisms, and (3) determining the annual loss of phosphorus from the sea through the harvest of fishery products. Chemical Analysis The organic phosphorus in the dried or partially ashed (8 hr at 500-600ºC) specimen was converted to inorganic forms by a sulfuric-nitric acid digestion. After digestion the residue was fumed clown to about half its volume to reduce a hy-product of the digestion reaction, nitrosyl sulfuric acid. This was necessary to prevent interference from the by­product in the subsequent phosphorus analysis. The sample was cooled and a portion of it diluted to the equivalent of about 10,000 mi per gram dried sample weight. Two sets of aliquot samples were prepared for analysis. One contained 1 mi of the diluted specimen mixture and the second, 3 mi. The samples of both sets were diluted to 25 mi with dis­tilled water. The analytical method employed was that described by Robinson and Thompson (1948). Control samples were prepared from KH2P04 and also from a dried powdered fish mixture of known phosphorus composition. The purpose of the latter was to detect interference due to the nitrosyl sulfuric acid in the samples. Each specimen was analyzed four times. The precision of the average of the four analyses per specimen was estimated to be 0.1 mg P per gram sample weight (dry basis). The analyses are tabulated in Table l. TABLE 1 Phosphorus content of certain fishes and shrimp Per cent of phosphoru1 Average weight Wet weight Dry weigbt No. of Wet Dry Standard Species specimens g g Average Average deviat.ion Lanternfish erg ('2) Abt. 4: 77. (Cited by Vinogradov.) McCay, C. :M., A. Tunison, Mary Crowell, D. K. Tressler, S. P. MacDonald, John W. Titcomb, and Eben W. Cobb. 1931. The nutritional requirements of trout and the chemical composition of the en tire body. Trans. Amer. Fish. Soc. 61: 58--79. Milone, Ugo. 1896. Composizione, valore nutritivo ed assimilahilita della carne muscolare dei pesci. Boll. Soc. Nat. Napoli 10 : 311. (Cited by Vinogradov.) Robinson, Rex J., and T. G. Thompson. 1948. The detennination of phosph11te in sea water. J. Mar. Res. 7: 33-41. Roche, J., and E. Bullinger. 1939. Recherches sur l'ossification. VII. La phosphatase du squelette (os, dents, dermatosquelette) chez les poisson osseux ou cartilagineux. Bull. Soc. Chim. biol., Paris. 21: '166-184. Sempolowsky, Leo. 1889. Untersuchungen von Seetieren auf ihren Gehalt an agrikultur-chemisch wichtigen Stoffen. Landw. VersSta., XXXVI, S. 61. (Cited by Atwater.) Vinogradov, A. P. 1953. The elementary chemical composition of marine organisms. Sears Founda­tion for Marine Research, Y ale Univ. 647 p. Weigelt, Curt. 1891. Die Abfiiller der Seefischerei; experimentelle Untersuchungen über deren Natur, Menge, Verarbeitung und Verwertung. (sonderbeilage zu den Mitteilungen der Sektionen f. Küsten und Hochseefischerei.)-Moeser, Berlin, 115 p. (Cited by Vinogradov.) Chaetognatha From the Texas Coast E. LOWE P1ERCE1 Department of Biology, University of Florida Gainesville, Florida Abstract Three genera and eleven species of chaetognaths were identified from collections made in the bays and along the Texas coast. No marked difference was noted between the faunas of the west coast of Florida and the Texas coast. Other studies show the same species of chaetognaths present along the coast from Cape Hatteras around the Gulf and extending into Central American waters. Sagitta tenuis, S. enfiata, and S. hispida were most numerous. lntroduction The chaetognath fauna of only a limited area of the Gulf of Mexico has been investi­gated. Although chaetognaths have been reported from the west coast of Florida and Cuba, (Ritter-Zahony' 1910, Pierce 1951, 1954, Suarez-Caabro 1955, and Tokioka 1955) there are no published reports on the Chaetognatha of the Texas coast. Not only does the Texas coast represent a very large area, but the interruption in the inshore salinity pattern produced by the Mississippi River poses a question concerning the similarity of arrow worms of the coastal waters of the eastern and of the western Gulf. During the summer of 1960, 1 had the opportunity of collecting plankton sarnples in a number of places in the Port Aransas area of Texas. As a result of a short trip to Veracruz, Mexico, during the same summer, 1 secured two more samples far down the Mexican coast. Also 1 was fortunate to obtain 62 plankton samples collected by Mr. E. D. McRae when he was employed in 1951 by the Texas Game and Fish Commission Marine Laboratory at Rockport, Texas. As a result of the 107 samples reported in this paper, the general pattern of the distribution of chaetognaths along portions of the Texas coast is apparent. Methods A variety of nets was used in making these collections. These included a Clarke­Bumpus Sampler and a 10 and a 16-inch net. Several types of netting were used but ali were fine enough to retain very small chaetognaths. Most of the samples were collected in shallow water with oblique tows from near bottom to the surface. Tows were usually of 10 to 30 minutes duration. Salinity· samples were taken and salinity determinations made by titration with silver nitrate. Plankton tows were made in the small bays north and south of Aransas Pass as seen in Fig. l. The northernmost tows were in Copano and Aransas Bays just a few miles north of Aransas Pass. The southernmost tows were ofI Port Isabel near the Mexican border. Two collections were made off Veracruz, Mexico, from an area where no chae­tognaths had been reported within 500 miles ( see insert, Fig. 1) 1 Visiting lecturer in NSF sponsored Advanced Subject Matter Institute in Marine Science at Port Aransas in 1960. Chaetognatha from the Texas Coast Fu;. l. Collecting stations along the Texas coast. Insert shows the two stations near Veracruz, Mexico. Results Three genera and eleven species of chaetognaths were collected along the Texas coast. The genera included Sagitta with eight species, Krohnitta with two species, and Pterosa­gitta with one species. These species are shown in Table 1 m order of decreasing abundance. TABLE 1 Chaetognaths collected along the Texas coast Bays 19 samples Aransas Pass 34 samples Coast 54 samples Species No. Times collected Per cent limes collected Times collected Per cent times collected Times collected Per cent times collected S. tenuis 5190 8 42 34 100 45 83 S. enfiata 1674 o o 19 56 40 74 S. hispida S. minima 385 191 4 o 21 o 8 1 24 3 22 12 41 21 K. pacifica 145 o o 2 6 23 43 S. serrato 105 o o o o 13 23 P. draco 16 o o o o 5 9 S. helenae 10 o o 3 9 4 7 S. lyra S. bipunctata K. subtilis 6 4 2 o o o o o o o o o o o o 1 2 1 2 4 2 Total 7728 Sagitta tenuis was the most abundant and the most widespread. 5190 specimens were found in all the samples. This species was present in 42% of the hay samples, 100% of the Aransas Pass samples, and 83% of the samples taken along the coast. lt occurred in water of salinities ranging from 29.l to 39.7 %o· lts apparent reduced incidence in the bays is partly the result of four samples taken in Corpus Christi Bay and the Laguna Madre which yielded no chaetognaths of any kind. In the northern section of the Laguna Madre (Fig. 1) where the samples were taken, the salinities ranged from 45.6 to 51.6 %0• Plankton generally was reduced, but not absent from these samples. The high salinity appeared to be the responsible factor for the absence of chaetognaths. If this is true, it points to an upper limit of salinity which these species do not tolerate in nature. Specimens of S. tenuis collected in this study agree in general morphological detail with individuals deposited in the U.S. National Museum by F. S. Conant who described the species (1896). There do not appear to be enough distinctive features in these speci­mens to warrant separating them into two species. Admittedly' in view of the systematic problems involved in the separation of S. tenuis and S. friderici comparative studies of specimens from widely spaced localities are needed. S. en/lata was second in abundance, although absent in the bays and clearly most abundant off the coast in stations 47 to 91. It was found in salinities ranging from 31.9 to 37.2 %o, but clearly its optimum habitat is the saline offshore water (Pierce 1951, 1953, and 1958). S. hispida is typically an inhabitant of bays and inshore water (Pierce 1951and1958). 1t was the only other species found with S. tenuis in the hay waters. 1t occurred in re­duced numbers in many of the stations located a number of miles from shore. Its presence offshore can in part be explained by the strong outflow of water from Aransas Pass. The salinity range of 31.6 to 37.2 %o in the coastal water where S. hispida was collected indicates appreciable dilution at times by hay water. S. helenae, eighth in abundance, occurred commonly along the coast and extended outward over the continental shelf (Pierce 1951, 1958, Bumpus and Pierce 1955). 1t was common along the Gulf and Southeastern Atlantic coasts. The other species, S. minima, S. serrawdentat,a, S. lyra, S. bipunctata, K. pacifica, K. subtilis, and P. draco, are customarily found over the outer portion of the continental shelf (Pierce 1953, Bumpus and Pierce 1955, and Owre 1960) and across the oceans. These have all heen collected in the shelf and ocean waters off the coast of the south· eastern Atlantic states. These species were almost entirely ahsent from hoth hay and pass water. Their occurrence in these samples is in agreement with other records of their distrihution. Association of Species Selected samples are tahulated in Table 2 to show the relative ahundance and associa· tion of the chaetognaths found in hay, pass, and coastal waters. In the bays, S. tenuis or S. hispida occurred in reduced numbers. In any one sample there were usually hut a few TABLE 2 Selected samples from bays, Aransas Pass, and coastal waters illustrating typical associations and relative abundance of species. Chart Salinity slation* Dale %,, Location Species 2 7 .March, 1951 32.0 Aransas Bay 7 S. tenuis 15 7July,1960 37.0 Aransas Pass 3 S. enfiata, 56 S. tenuis, 1 S. hispida 32 19 July, 1960 32.6 Aransas Pass 19 S. enfiata, 12 S. tenuis 49 12April,1960 32.9 Coast, 2 mi. S.E. 91 S. hispida, 4 S. tenuis entrance Aransas Pass 58 30 July, 1951 36.3 Coast, 9 mi. S.E. 3 S. enfiata, 42 S. tenuis, entrance Aransas Pass 1 S. helenae, 6 K. pacifica, 20 S. hispida 75 20 July, 1951 36.5 Coast, 21 mi. S.E. 21 S. enfiata, 5 S. hispida, entrance Aransas Pass 3 S. serrato, 18 S. tenuis 90 1 August, 1951 36.3 Coast, 40 mi. S.E. 1 S. bipunctata, 3 S. serrato, Aransas Pass 27 S. enfiata, 2 K. pacifica, 27 S. minima, 11 P. draco 100 3 August, 1951 36.5 Coast, 17 mi. E. 6 S. enfiata, 2 S. tenuis, Laguna Madre 1 S. hispida, 5 K. pacifica 26º4' N., 97°0'1' W. 101 3 August, 1951 Coast near entrance 3 S. hispida, 20 S. tenuis to Port Isabel 107 19 July, 1960 Coast, 12 mi. S.E. 4 S. enfiata, 20 S. tenuis, Veracruz, Mexico 1 S. hispida • Stalioos can be louted in Figure l. members of either species. Aransas Pass samples commonly contained both S. hispida, S. tenuis, and occasionally S. enfiata. The presence of the last species indicates an influx of offshore water in the pass. The absence of S. serratodentata and S. bipunctata is a strong indication that only a limited amount of offshore water was introduced into the pass during the period when these samples were taken. The group of species characteristic of the offshore Gulf water included S. bipunctata, S. lyra, S. mínima, S. serrawdentala, K. pacifica, K. subtilis, and P. draco. Few of this group appeared in samples closer than six miles to Aransas Pass. As shown at stations 53, 75, and 90 in Table 2, most of these appeared together in many of the offshore stations. Temperature and Salinity During the summer of 1960, temperatures close to 30º C. were usually recorded in the surface waters of the bay's, passes, and coastal water. From the limited data available, there is no indication what effect temperature may have on distribution along the coast of Texas, nor are the precise effects of salinity clear. The high salinity of the Laguna Madre (45 to 51 %o) did appear to prevent chaetognaths from living there as none at all were found in the four samples from this area. In the remainder of the samples, salinities of severa! parts per thousand both below and above 35 %o were encountered in the hay, pass, and coastal waters. The fact that many of the samples were taken in areas of shallow water and strong tides probably masked the effect that salinity might have exerted had there been a chance to observe stabilized salinity concentration in such places. Discussion There does not appear to be any striking difference in the distribution of chaetognaths between the eastern and western portions of the Gulf of Mexico. S. hispida and S. tenuis are common inshore species in Florida and Texas. S. helenae appears to be more abun­dant along the west coast of Florida than along the Texas coast. Since this species occurs principally in the waters over the continental shelf, the wider shelf off the west coast of Florida may be a factor favoring a larger population there. More extensive studies have been published on the arrow worms off the Southeastern Atlantic states (Pierce 1953, 1958, Bumpus and Pierce 1955, and Owre 1960). These report the presence of the same species under conditions comparable to the Texas coast. North of Cape Hatteras the chaetognath fauna changes abruptly. South of Cape Hatteras, over the continental shelf from North Carolina to Texas, there does not appear to be any marked change in the distribution of chaetognaths. The two samples taken off Veracruz, Mexico, indicate that this same fauna extends along the Mexican coast. Moreover, Suarez-Caabro and Madruga (1960) recorded the presence of S. hispúla, S. terwis, S. enflata, and other species off Honduras. All of the species collected by Surez-Caabro were present along the Texas coast. lt is now apparent that the coastal water south from Cape Hatteras, the Gulf of Mexico, Cuba, and portions of Central America support a similar chaetognath fauna. Acknowledgments 1 am indebted to Dr. Howard T. Odum, Director of the lnstitute of Marine Science, for allowing me the use of laboratory' facilities and a collecting boat at Port Aransas, and to Mr. Howard Lee, Director of the Texas Game and Fish Commission Marine Laboratory at Rockport, for the use of his facilities. Miss Karen Hodges, my assistant for the summer of 1960, was most helpful in the sorting and enumeration of many of the chaetognaths reported in this paper. Literature Cited Bumpus, D. F., and E. L. Pierce. 1955. The hydrography and the distribution of chaetognaths over the continental shelf off North Carolina. Pap. Mar. Biol. and Oceanogr., Deep-Sea Res., Suppl. to 3: 92...:109. Chaetognatha from the Texas Coast Owre, H. B. 1960. Plankton of the Florida current. Part VI. The chaetognatha. Bull. Mar. ScL Gulf Carib. 10(3): 255-322. Pierce, E. L. 19!Jl. The chaetognatha of the west coast of Florida. Biol. Bull. 100(3): 2~228. ----. 1953. The chaetognaths over the continental shelf of North Carolina with attention to their relation to the hydrography of the area. J. Mar. Res.12(1): 75-92. ----. 1954. Notes on the chaetognaths of the Gulf of Mexico. Fish. Bull. U. S. 55(89): 227-3'29. ----. 1958. The chaetognatha of the inshore waters of North Carolina. Limnol. Oceanog. 3(2): 166--170. Ritter·Zahony, R. von, 1910. Westindische Chatognathen Zool. Jb., Suppl 11 (2): 133-143. Suarez·Caabro, J. A. 1955. Quetognatos de los mares Cubanos. Mem. Soc. Cubana Hist. Nat. Felipe Poey, Univ. Habana 22(2): 125-180. Suarez·Caabro, J. A., and J. E. Madruga. '1960. The chaetognatha of the northeastern coast of Honduras, Central America. Bull. Mar. Sci. Gulf Carib. 10(4): 421-429. Tokioka, T. 195'5. Notes on sorne chaetognaths from the Gulf of Mexico. Bull. Mar. Sci. Gulf Carib. 5 (1) : 52-65. An Ecological Survey of the Lower Laguna Madre of Texas, 1953-19591 JOSEPH p. BREUER Marine Biowgist Texas Game and Fish Commission Abstract Hydrographic data and annotated comments on the distribution and habits of species are presented for the Lower Laguna Madre of Texas, a shallow, hypersaline marine hay extending 76 miles north of the Rio Grande delta. In summer, waters of the Gulf move northward through the lagoon with increasing salinity due to evaporation. The variety of species in the plankton and bottom communities diminish with distance from the pass. In winter, flow is southward. A population of commercial oysters, Crassostrea virginica, near the pass apparently is adapted to high salinity conditions. Sorne ecological effects of man-made changes are described, including the effects of opening Port Mansfield Pass, the isolation and silting of South Bay due to spoil, and the management of the Río Grande River during floods. Movements of year classes of game fishes are described. lntroduction The Laguna Madre of Texas (Fig. 1) is a generally shallow, hypersaline hay area on the South Texas coast extending from Corpus Christi Bay south to the Rio Grande River. This hay has long been important in commercial fisheries production and in recent years, with the general decline in commercial production of other areas of the coast, has be­come the leading producer of such important hay fishes as the black drum, redfish, and the spotted trout. Since World War 11, this area has also become important to hay sports fishing. This report concerns an ecological survey made in the Lower Laguna Madre from September of 1953 to September of 1959. For the purpose of comparison, an effort was made to follow as closely as possible the general outline and reporting procedure used in two previous papers on other sections of the Laguna Madre: An Eco/,ogical, Survey of the Upper laguna Madre of Texas (Simmons, 1957) and An Ecological, Survey of Baffin and Alazan Bays, Texas (Breuer, 1957) . Regular collections were made at thirteen sta­tions (Fig. 1 )including representative habitats and depths. Data are presented on hy­drography, species, fish mortalities, and effects of the Port Mansfield Pass. PREVIOUS INVESTIGATIONS There have been few investigations in the Lower Laguna Madre area. Daugherty from 1948 to 1950 initiated preliminary investigations at Port Isabel, and Miles continued these investigations from 1951 to 1952 and reported on fish movement and migrations. Whitten, Rosene and Hedgpeth ( 1950) reported on the invertebrate fauna of the Brazos Santiago jetties. Carlgren and Hedgpeth ( 1952) described severa! anthozoans from Brazos Santiago Pass, Port Isabel, and South Bay. Hedgpeth (1953) discussed com­ 1 Contribution No. 50 from the Marine Laboratory, Texas Game and Fish Commission, Rockport, Texas. An Ecological Survey o/ the Lower Laguna Madre ·~ \ ' F1c. l. Lower Laguna Madre of Texas, with principal sampling stations, Nos. 13-25. munity relationships in South Bay. Shepard and Rusnak ( 1957) and Rusnak ( 1960) mapped the bay sediments and described other geological features. Parker (1959) con· tributed significant knowledge on the macroinvertebrate assemblages of the area. Other literature of value to the completion of this study included Burkenroad (1951), Collier and Hedgpeth (1950), Gunter (1950), Hedgpeth (1950), and Simmons and Breuer (1962). DESCRIPTION OF AREA The Lower Laguna Madre (Fig. 1) is located on the south Texas coast from a point 11 miles north of the southern boundary of Kenedy County south to the Río Grande, an air­line distance of about 74 miles. It is bounded by Padre and Brazos lslands on the east and by the Texas mainland on the west. The lagoon is bisected by the lntracoastal Canal from the northern end south to Port Isabel. The Brownsville Ship Channel extends from the jettics of Brazos Santiago Pass which separates Padre and Brazos Islands, west to Port Brownsville. Natural islands are abundant near the Arroyo Colorado delta, but many are surrounded by mud flats. The Lower Laguna Madre area can be divided into four parts (Fig. 1). The northern­most area, Redfish Bay, (not to be confused with Redfish Bay near Port Aransas) ex· tends from the landlock or land-cut south to approximately four miles south of Port Mansfield. The middle area extends from this point south to Three Islands. The area known as Port Isabel Bay extends from Three Islands south to the Brownsville Ship Channel. South of this channel is South Bay. With changing water levels due to wind variations, there is no sharp demarcation be­tween land and water. For the purpose of describing land and water areas, U.S. Coast and Geodetic Survey charts 896, 897, and 898 were used. These charts show yellow for land, blue and white for water, and green for flat lowland often inundated by water. See Fig. 2. In the northern end of the hay there is severe filling dueto encroachment of sand from the island ( Fig. 3). Filling in at the landcut is complete, and the entire hay area is coro· posed of shallow flats, subject to inundation only at times of high water. These extend west from Padre lsland 1 to 21/z miles from the northern extreme of Redfish Bay south to Three lslands. From Three lslands south to Brazos Santiago Pass, these flat, exposed areas are less than one-fourth mile in width. Along the mainland shores, the boundary of land and water is definite in the Redfish Bay area. The mainland is semi-arid pasture land with many oak motts. Water depths of over one foot extend to within a few yards of shore. There are considerable areas of flats suhject to inundation along the mainland shore of the entire middle portion due to deltas built up by the North Floodway, Arroyo Colorado, and the Cayo Atascosa. The mainland shores of Port Isabel Bay are well-defined, as are those of Redfish Bay. The South Bay area is surrounded by exposed flats resulting from siltation from the Río Grande and dredge spoil from the Brownsville Ship Channel. Water area of Redfish Bay is about 53,000 surface acres, which is normally covered by water. About one-third of this area, or 18,000 acres, is six feet deep or more at mean low tide. This deep water forros a long, narrow, irregular patch paralleling the shore some 13 miles through Redfish Bay. The lntracoastal Canal was dredged through this deep water, but the resulting spoil banks are submerged and have little influence on water transport in the area. This deep water, along with the absence of substantial spoil banks, causes this area to be quite rough in either north or southeast winds. The middle area oontains sorne 47,500 water acres. With the exception of the lntra· coastal Canal, there is no water over three feet in depth, and the average is closer to one foot. An Ecological, Survey of the Lower Laguna Madre -- Ktn t d1 Co111111 ·-·-------------· --Wdlocv Co11n 1v cº"'••o-::-~o~;---------­<..º , ' º'º \.. A 10 1 co1 --~'.'~! e,,,,, r··, Londond Shorel•nt ·• , . ...t --­E~poitd Fla lt (1..b1 111 •flnudol.,HI ) ~ LO WER LAGUNA MADRE F1G. 2. Depth and distrihution of flats in the Lower Laguna Madre. The Port Isabel Bay area (Fig. 4) contains another 47,500 acres of water, although the average depth is from three to four feet, much more than the middle area. The only sections with depths greater than six feet, with the exception of the lntracoastal Canal ~ •, dé' ~ "'-, ' ~· ..~~~~1 ..?. Ken•dy Co unty ---­-----­----------------Willocy (;o.,n t y -~:·~~~"" y··,Cg"''' º" ;o::;--------­(,,o • Lo Quno lllOICOIO Cl<1)' •Y Son d "c. < F1c. 3. Type of sediments in the Lower Laguna Madre after Shepard and Rusnak (1957). and the Brownsville Ship Channel, are several areas in the vicinity of the Queen lsabella Causeway and the Padre Island Coast Guard Station. South Bay at present contains sorne 2,500 surface acres of water with a maximum depth of three feet and an average of 18 inches. An Ecological Survey o/ the Lower Laguna Madre LO WER LAGUNA l'iow1icol •" ' ' lJ--~ ,,.. \\ " ",,,,\b .. \\ ~\ " \\ ''o ' " " '~\\ ·· 1:, ' 11 " 'o PORT o .. \\ \\ \\ \\ \\ \\ \~ 0 \\ \\,, \\ 0 \,,. \\ \\ \\,, ISABEL BAY '\~, © \\ \\ © © \ MADRE '\~,n ::-_,__,.,~o-"'-.) @ % o >!'~ 'i '­< 11 1 GULF OF MEXICO ' ~"""'"'''"""'' ,1=-;;:::.::_: ª'º'º' so~T• aeo F1G. 4. Map of the Lower Laguna Madre in the vicinity of the Brazos Santiago Pass. Numbers in circles are experimental oyster reefs. The lntracoastal Canal, extending 63 miles from Port Isabel to the landcut, has a bol· tom width of 125 feet and is 12 feet deep. The Brownsville Ship Channel is fifteen miles long, extending from Brazos Santiago Pass to Brownsville, and is from 100 to 1,000 feet wide and 36 feet deep. The approach to this channel through the pass is 300 feet wide and 38 feet deep. The twenty·five miles of dredged Arroyo Colorado, opening Port Har· lingen, is 125 feet wide and nine feet deep. The five miles of channel connecting Port Mansfield with the Gulf of Mexico is 100 feet wide and 12 feet deep. From Port Mansfield south to Three Islands, the mainland shore is of a delta-type built up in the past by flood outlets of the Rio Grande. These waterways are now known as the North Floodway, Arroyo Colorado, and Cayo Atascosa. From Three lslands south to Port Isabel, the mainland shore is again well-defined. Two hundred years ago an arm of the Rio Grande emptied into South Bay. Since then, the river has changed its course to empty into the Gulf of Mexico. Boca Chica Pass was closed by nature, with consid­able belp by man, at the south. The North Floodway, which empties into the Laguna Madre about fourteen miles south of Port Mansfield, normally carries drainage from much of the Rio Grande Valley. Excess rainwater and irrigation water is drained from the land via this floodway. The volume of water carried is normally very low. The Arroyo Colorado is also a floodway and carries drainage and excess rainwater from other portions of the watershed. Both the North Floodway and the Arroyo Colorado connect with the Rio Grande near Mission, Texas, and can carry flood waters from the Rio Grande when this river reaches flood stage. The Cayo Atascosa also carries drainage and irrigation water into the hay. The Atas­cosa Wildlife Refuge impounds most of this water, however, and seldom does any reach the bay. The Cayo empties into the Arroyo Colorado about two miles west of the lntra­coastal Canal. There is no other source of fresh water stream flow into the hay area. In fact, except in times of flooding, the amount of drainage into the Lower Laguna Madre must be con­sidered negligible. HlSTORY Prior to 1935, with the exception of Port Isabel Bay, the Lower Laguna Madre was a primitive area known mainly by commercial fishermen. Port Mansfield, Arroyo City, Holly Beach, Laguna Vista, lntracoastal Canal, the dredged Arroyo Colorado, the Atas­cosa Wildlife Refuge, the Naval Air Station, Brownsville Ship Channel, Port Brownsville, Queen lsabella Causeway, and the Cameron County Park on Padre Island did not exist. In 1948 the lntracoastal Canal was dredged from Corpus Christi Bay to Port Isabel. This waterway provided a safe boat route for the entire length of the Laguna, and sports fishing increased. With Port Isabel as the terminus of the intracoastal waterway and the Brazos Santiago Pass as an outlet into the Gulf of Mexico, the Brownsville Navigation District completed the deep-water channel fifteen miles inland to form the new Port of Brownsville. The Cameron County Navigation District dredged the Arroyo Colorado from the lntracoastal Canal, through Rio Hondo, and at its terminus built the Port of Harlingen. Willacy County formed a Navigation District, built Port Mansfield and con­nected it with the Intracoastal Canal. Recently a channel and pass were dredged to the Gulf, and jetties have been constructed on the Gulf entrance. In spite of these modifications, the Lower Laguna Madre remains largely an unpopu­lated hay area. Most of the adjoining lund is owned or controlled by government or large prívate concerns such as the King Ranch, U.S. Fish and Wildlife Service, and the U.S. Navy. An Ecological Survey of the Lower Laguna Madre Hydrography ÜRCULATION AND SALINITY Data on salinities obtained by the author, at stations in the Lower Laguna Madre (Fig. 1) are presented in Table l. Data on wind and rainfall, obtained from the records of the Weather Bureau, U. S. Department of Commerce, are given in Table 2. Sorne discussion of the distribution of wind and rainfall provides an explanation for the salinity distribu­tion. TABLE 1 Salinities in the Lower Laguna Madre in %c Stalions Date 13 14 15 16 17 18 19 20 21 22 23 24 25 June,1954 ······ --· ·· .... --­· · · July, 1954 3.2 34.5 35.2 36.6 35.8 39.1 40.5 40.6 37.7 34.0 '39.0 40.7 4!2.7 August, 1954 35.0 34.7 36.4 41.5 42.0 41.l 43.7 44.3 September, 1954 .... ···· ·­ .... October, 1954 5.1 32.'2 28.5 33.7 3'3.7 33.5 29.8 27.9 38.4 40.0 39.9 4!3.5 43.0 December, '1954 11.5 33.2 33.'2 32.5 ··· ·­ 33.5 39.0 41.1 45.1 48.8 51.'l-W February, 1955 9.6 36.8 34.8 36.6 36.5 35.3 37.3 40.0 42.8 48.7 52.1-W May,1955 14.0 35.0 36.0 40.0 43.0 42.0 43.0 48.0 46.0 48.0 48.0 55.0 June,1955 13.4 35.5 35.7 38.6 36.2 ---­ 39.8 44.6 44.5 44.4 45.2 August, 1955 9.8 41.3 39.0 41.0 39.6 42.8 44.6 44.2 46.8 45.2 47.2 47.4 47.8 September, 1955 39.5 30.0 26.'l 23.5 29.2 24.9 25.5 25.1 27.0 November, 1955 36.2 35.8 4:2.5 30.1 31.7 28.8 23.4 25.0 28.3 28.4 29.0 January, 1956 38.1 '35.6 3'1.9 32.2 31.l 31.1 23.3 35.3 32.1 37.1 28.7 39.5 March,'1956 6.6 35.1 35.6 35.4 35.4 39.1 36.4 34.0 35.0 32.4 36.6 39.'2 40.6 June,1956 '10.4 37.7 40.6 35.2 35.4 21.9 41.0 40.6 41.6 41.4 4l'2.2 August, 1956 20.8 38.5 41.4 44.5 44.0 47.0 47.'2 47.5 September, 1956 16.9 39.1 38.3 41:1 41.4 413.9 43.7 '41.4 412.1 46.6 ...... TABLE 2 Wind and rainfall at Raymondville, Texas Prevailing wind Frequency Mean Rainfall Month Direclion per cent velocily, mph incbes September, 1953 NW 13 10.3 0.35 October, '1953 ESE 22 10.6 1.95 November, 1953 SE 12 10.1 3.46 December, '1953 NW 17 1'2.5 0.84 January, 1954 SE 25 12.9 0.26 February, 1954 SSE '17 13.0 0.09 March, 1954 SSE 28 15.6 0.55 April, 1954 SE 39 16.1 4.07 May, 1954 ESE '31 14.1 2.27 June, 1954 SE 47 15.3 2.87 July, 1954 SE 40 '11.8 0.21 August, 1954 SE 3'1 11.6 1.27 September, 195'4 SE 15 9.3 4.05 October, 1954 SE 20 9.2 3.74 November, 1954 NW 17 10.8 1.69 December, 1954 January, 1955 SE SE 18 18 10.6 12.2 0.11 1.58 February, '1955 SE 24 14.2 0.37 March, 1955 SSE 31 '16.2 0.03 April, 1955 SE 27 15.4 0.16 May, 1955 SE 42 '15.7 5.61 TABLE 2-Continued Wind and rainfall at Raymond\'ille, Texas Pnvailing: wind Frequency Mean Rainfall Month Direelion per cenl '"elocily~ mph inches June, 1955 SE 39 13.6 0.30 July, 1955 SE 34 11.3 4.03 August, 1955 SE 29 9.8 2.79 September, 1955 E 17 9.5 15.90 October, '1955 SE 15 9.6 1.16 No"ember, 1955 SSE 24 '13.7 0.63 December, 1955 NNW '15 10.9 0.57 January, 1956 SSE 15 11.6 0.03 February, 1956 SSE 23 14.9 1.23 March, 1956 SE 27 14.0 April, 1956 SE 22 14.8 4.32 May, 1956 SE 43 '15.2 2.76 June, 1956 SE 43 1'2.9 1.05 July, 1956 SSE 41 14.4 0.04 August, 1956 SSE 33 13.9 1.20 September, 1956 s 17 8.4 2.21 October, 1956 SSE 11 8.0 0.64 November, 1956 SSE 18 13.3 0.47 December, 1956 SSE 19 9.8 1.00 January,1957 SSE 32 15.0 0.05 February, 1957 SE 18 13.0 2.55 March, 1957 SSE 24 15.1 2.57 April, 1957 SE 33 16.9 3.23 May,1957 SE 44 16.l 2.14 June, 1957 SE 37 13.5 4.66 July, 1957 SE 44 13.5 0.56 August, 1957 SE 34 1'2.4 0.30 September, 1957 SE 17 '12.1 1.50 October, 1957 SE 17 13.0 1.30 November, 1957 SE 17 13.9 3.48 December, 1957 SE 21 13.0 0.11 January, 1958 NW 20 12.9 7.33 February, 1958 SE '18 13.3 3.91 March,1958 SE 19 12.2 0.71 April, 1958 SSE 27 13.5 0.23 May, 1958 SE 17 9.9 1.77 June, 1958 SE 32 12.6 2.17 July, 1958 SSE 42 1'2.3 3.27 August, 1958 SSE 37 11.4 September, 1958 SE 13 9.3 4.4~ October, 1958 NW 21 '10.5 10.94 November, 1958 NNW 16 9.4 1.80 December, 1958 NNW 30 10.6 l.'25 January, 1959 NNW 18 10.6 'l.44 February, 1959 NNW 19 u.o 2.69 March, 1959 SSE 17 11.8 0.13 April, 1959 SSE 25 11.7 1.20 May, 195º SE 38 '13.0 2.15 June, 1959 SSE 30 11.0 1.43 July, 1959 SSE 35 10.0 0.4ó The lntracoastal Canal extending the entire length of the Lower Laguna Madre, along with the opening to the Gulf of Mexico at Brazos Santiago Pass at the south, and the opening through the land-cut to the Upper Laguna Madre to the north, provides principal water exchange. It is this circulation that prevents excessive hypersalinity. Current di­rection varies with the seasons. During the summer months, the prevailing wind is from the south and southeast. These prevailing winds, along with the south-to-north shore cur­ An Ecological Survey o/ the Lower Laguna Madre rent in the Gulf, cause the water of the Gulf to enter the hay area through Brazos Santiago Pass, flow north through the entire Lower Laguna Madre and through the land-cut to the Upper Laguna Madre area. During the winter months, the prevailing wind is from the north, and the entire situation is reversed. South and southeast winds prevail through most of the year, however, and the resulting current affords excellent water exchange in the area. However, the water entering the system is from the Gulf of Mexico, with a salinity of 32 to 35 9"00, and not fresh river water. The freshest water in the Lower Laguna Madre, proper, is adjacent to Brazos Santiago Pass. The salinity gradually increases as the water travels north. Highest salinities encountered are at the northern end of Red· fish Bay. During the summer, saEnity variations from the two ends of the system may be as high as 15 %0 , due to the heavy rate of evaporation. This variation is somewhat less in the spring and fa]] because of the lower evaporation rates. Extremely high rate of evaporation in the landlock and Upper Laguna Madre during the summer and fa]] months causes a high salinity in these waters. The prevailing northerly winds during the winter months bring this hypersaline block of water south into Redfish Bay. Thus, the highest salinity in the upper Laguna appears in August, (Sim­mons, 1957) while in the lower Laguna it is in February (Table 1). In both cases, hyper· salinity is due to lack of adequate circulation, extensive areas of shallow water, and the high rate of evaporation in the Upper Laguna Madre area. The newly completed channel and pass from Port Mansfield to the Gulf of Mexico has had sorne effect on water currents in the area. The project was completed in 1958, using patented concrete tetrapods for jetty construction. By 1959, a bar had built up between the jetties, making the pass no longer navigable, although it remained functional until July of 1960, when the pass was purposely closed to facilitate construction of new im­pervious jetties. At this writing, jetties and channel dredging are complete, with the opening of the pass occuring in May, 1962. The effect of the pass, while open, on the currents of the area has already been estab­lished. In the prevailing souheast wind, the water enters the Brazos Santiago Pass through a minimum cross-section of 43,200 sq. ft., and the water leaves the area through a land-cut with a minimum cross-section of 3,600 sq. ft. These measurements were taken from the U. S. Corps of Engineers plans and specifications. The Port Mansfield Pass provides a valve for the head of water built up in Redfish Bay. The current flows out from hay to Gulf. Only during periods of north winds, and the resulting north-to-south cur­rent, is the situation reversed (numerous personal observations). The prevailing current, then, through the two passes, is exactly opposite. The pass at Port Mansfield stabilizes the salinity in the Redfish Bay area. TrnAL EFFECTS The high set of the Gulf in the spring and fall causes the water leve! of the area to rise sharply from 12 to 18 inches. The wt:ter leve] also varies with the diurna! tides and is most noticeable at Port Isabel. The daily effect, however, decreases away from the pass, or to the north. These tides may complement the steady current. An incoming wind cur· rent in Port Isabel Bay can be very swift or slow, depending on whether the tide is com· ing in or out. As one travels north, the effect of tide on current becomes less noticeable. The effect at Three Islands is slight, and at Port Mansfield, is negligible. No correlation exists between temperature and any other hydrographical or meteorological factors, other than salinity through rate of evaporation. Evaporation is greater during the months when temperatures are the highest and the days longest; higher salinities result. Since higher temperatures exist in the summer months, the variation in salinity from Brazos Santiago Pass to the land-cut is greater during these months. The Arroyo Colorado and North Floodway are both flood control overflows for the Río Grande. These are seldom used since the great dams have been built in the Rio Grande. In the fall of 1958, these two channels carried an estimated 5,000,000 acre feet of water into the hay fromt he flooding Rio Grande, which otherwise would have caused great destruction in Brownsville and other Valley cities. This influx of fresh water greatly af­fected the hay area, and its effect was noted for at least 6 months. Species normally con­fined to the brackish Arroyo Colorado, such as threadfin herring and alligator gar, were present in the hay, proper. For example, salinity at Three Islands in August, 1958, was 35.6 %o. After the flooding, salinities dropped to 13.2 %o in November, 1958, rose to 17.4% in December, and to 31.2% inAprilofl959. Turbidity of the waters of the Lower Laguna Madre varied considerably, and observa­tions made in the study seem consistent with the following interpretations of the role of wind, current, tide, water runoff, depth of water, and bottom type. The most important factor was the presence or absence of bottom vegetation. Water overlying a bottom devoid of vegetation was seldom clear, su ch as the deeper waters of South Bay; anda bottom with heavy growth of submerged vegetation was seldom turbid, such as in the Green Island­Three Islands area. In general, turbidity in shallow water was observed to be caused by wind; in deeper water, by current and tide. Runoff from the surrounding watershed was found to be turbid if the flow was heavy, as evidenced by the flooding in the fall of 1958. Turbidity was greater in waters over a sih or clay bottom, such as in the area at the old mouth of the Arroyo Colorado. Turbidity was less over a sand bottom, as along the hay side of Padre Island (Shepard and Rusnak, 1957). In general, the waters of South Bay were very turbid over barren bottoms, but clear among heavy submerged vegetation, as observed on numerous occasions. Water also was unusually clear between the Browns­ville Ship Channel and Queen lsabella Causeway, where there was heavy vegetation, in spite of the strong currents. Water was also clear from the Causeway north to Three Islands between the lntracoastal Canal and Padre Island. In addition, there were other small areas of comparatively low turbidity. SALINITY AND SPECIES VARIETY Among the hay fishes, the number of species prescnt increases and the number of in­dividuals o·Í each species decreases, as the salinity of the hay water approaches Gulf salin­ity, either from a fresh or from a hypersaline condition. This is true of invertebrates and vegetation as welL The greatest number of floral and fauna! species is found at the ap­proach to the Brazos Santiago Pass, for here, both Gulf and hay forms are interspersed. As the distance from the pass is increased, and the salinity deviates from Gulf salinity, the number of species decreases, but the total number of individuals of the remaining species increases. Details are cited in the following annotated list. Annotated Notes on Occurrence of Species Although far from complete, the listings that follow provide a synopsis of sorne of the biota during the study period, 1953-1959. An Ecological, Survey o/ the Lower Laguna Madre Sorne of the literature used, which was valuable in the identification of species, was Humm and Caylor (1957) , Freese (1952), Hartman (1951), Gunter (1945), Pearson (1929), Ladd (1951), and U.S. Department of Interior (1954) . PLANTS Almost all of the plants are relatively dormant during the winter months. Brown and red algae begin to appear in February. The grasses start to show growth in March. Maximum growth for all types appears in June and July. The decay of alga! forms and the defoliation of the grasses coincide with the high water temperatures of August and September. AH of the red and brown algae of the area are found south of Three Islands in salin­ities of less than 40 %0 • Cymodocea manatorium and Thmassia testudínum also occur in South Bay and in the vicinity of Port Isabel at ornear Gulf salinity. In spite of the strong bay current capable of carrying all Gulf plankton forms through­out the entire bay system, most species of diatoms were found near the pass. Sorne genera such as Stephanopyxis, Rhizosolenia, Chaetoceros, Fragílaria, and Thalassiothrix were found only near Brazos Santiago Pass. There were exceptions, such as Licmophora, Nitzschia, and Coscinodiscus, which were found at all stations. Navícula was most com­mon in brackish waters. The salinity range in this area apparently did not affect the dinoflagellates. The following list is incomplete, as identifications of prepared slides and micropho­tographs are incomplete. The species listed in the Chlorophyta, Phaeophyta and Rho­dophyta are from a single incidental sampling, identified by Dr. E. Y ale Dawson, Allan Hancock Foundation, University of Southern California, and do not purport to be a complete list of algae for the area. PHYLUM CHRYSOPHYTA CLASS BACILLARJOPHYCEAE ÜRDER CENTRALES Hemídiscus sp. Rare at station 15. Stephanopyxis palmeríana (Greville) Grunow. Rare at station 15 in January. M elosira sp. Rare at station 15. Coscínodiscus sp. Found at all stations, apparently more common in Port Isabel Bay. Least abundant in summer. Rhizosolenía sp. Common at stations 14 and 15 near Brazos Santiago Pass during sum­ mer months. Chaetoceros sp. Found abundant only in January at stations 14 and 15 near the pass. Bíddulphía sp. Taken only at stations 14 and 15 at all times, but never abundant. ÜRDER PENNALES Fragilaria crotonensís (A.M. Edwards) Kitton. Rare, found at station 14 in August. Nítzschia sp. Scattered over most stations from March through May, not abundant. Striatella sp. Found from South Bay to Port Mansfield, most common in north Port Isabel Bay in August. li.cmophora sp. Found from March through August at most stations, common at station 17 in August. Thdasswthrix sp. Common at station 14 in March. Asterionella japonica Cleve. Very common in Gulf surf at Brazos Island in September. Thalasswnema nitzchwdes Grunow. Taken in Brazos Santiago Pass in May. Synedra sp. Station 15 in February. Gyrosigma sp. Station 14 in March. Pleurosigma sp. Station 14 in March. PHYLUM CHLOROPHYTA Enteromorpha fiexiosa J. Agardh. Common near Port Isabel. Ulva sp. Common near Port Isabel. Cla,dophora sp. aff. C. dalmatica Kutzing. Common in Arroyo Colorado in late spring. Acetabularia crenulata Lamarck. Found throughout the area attached to marl and dead shells. PHYLUM PHAEOPHYTA Di.ctyota cervi.comis Kutzing. Found in Port Isabel Bay in summer months. Sargassum sp. Entered passes in spring months; common then in Port Isabel Bay, Por\ Mansfield Pass, and on Gulf beaches. PHYLUM RHODOPHYTA Hypnea cervicomis J. Agardh. Common at stations 15 and 16. Corallina granifera Ellis & Solander. Taken in.Port Isabel Bay in late spring. Gracilaria blodgettii Harvey. Very common from Port Isabel to Three Islands from April to September. PHYLUM SPERMATOPHYTA Cymodocea manatorum Aschers. "Manatee grass," a dark green, reed-like grass com­mon in the Port Isabel area in the vicinity of Brazos Santiago Pass. Diplanthera (Hadoluli) wrightii Aschers. "Shoal grass" was present to sorne extent over almost all of the Laguna Madre area, the most common and abundant vegetative type. Ruppia maritima Linneaus. "Widgeon grass" was found along the lntracoastal Canal from Three Islands north to Port Mansfield and in the old bed of the Arroyo Colo­rado. Halophila engelmanni Aschers. This small plant was found sparingly with Diplanthera in the Three Islands-Green Island area. Characteristically there are three pairs of leaves at the apex of the branch. Thalassia testudinum Konig. "Turtle grass," in vast meadows, occurred in South Bay interspersed with Cymodocea manatorum, both north and south of Queen lsabella Causeway. An Ecological, Survey o/ the Lower Laguna Madre PHYLUM PROTOZOA CLASS MASTIGOPHORA ÜRDER DINOFLAGELLIDIA Dinoflagellates occurred at ali stations at ali times of the year, although never in large numbers. Ali species were found throughout the area, most abundant near passes. Peridinium depressum Bailey. Ceratium fuscus (Ehrenberg) Du Vardin. Ceratium macroceros (Ehrenberg) Vanhoffen. Certatium tripos (O. F. Müller) Nitzsch. Ceratium /urca (Ehrenberg) Du Vardin. PHYLUM PORIFERA Numerous sponge specimens have been collected near the mouth of Brazos Santiago Pass, but no identifications have been made at this time. PHYLUM COELENTERATA CLASS HYDROZOA ÜRDER HYDROIDA Nemopsis bachei L. Agassiz. Common in winter months throughout the entire area. Eudendrium sp. The specimens collected were examined by C. E. Cutress of the Smith­sonian lnstitution and reported by him to be an unknown species, probably new to sc1ence. Aglaophenia late-carinata Aldmann. This hydroid was common, attached to floating Sargassum weed. CLASS ScYPHOZOA ÜRDER RHIZOSTOMEAE Stomolophus meleagris Agassiz. The "cabbage head" was found occasionally in the Port Isabel area but was not nearly so common as in other areas of the Texas coast. ÜRDER SEMAEOSTOMEAE Aurelia aurita (Linnaeus). Fairly common throughout the area, more prevalent during winter months. CLASS ANTHOZOA ÜRDER AcTINIARIA Much more work is needed on this order, particularly on forms associated with the oyster reefs, jetties, and sea walls in the Port Isabel area. Hedgpeth reported Anthopleura krebsi as the common form on the Brazos Santiago jetties. Cal,liactis tricolor (LeSueur) . Common on the sea walls at Port Isabel and attached to large shells. Paranthus rapiformis (Le Sueur). Two specimens taken by shrimp trawl at the base of Brazos Santiago jetties, adj acent to Brownsville Ship Channel. ÜRDER MADREPORARIA Astrangia sp. Severa} living colonies have been found attached to the submerged con· crete pilings of the Queen Isabella Causeway at Port Isabel. This coral has been very common on the north jetty at Brazos Santiago Pass. Skin divers have taken hundreds of heads, since the spring of 1960, ranging in size from that of a golf hall to that of a basketball. PHYLUM CTENOPHORA Beroe ovata Chamissa and Eypenhardt. Very young specimens taken during late winter and early spring, adult specimens common in summer. PHYLUM ANNELIDA Branchiomma nigromaculata (Baird). Represents an extension of range for the species. Dr. Olga Hartman states that B. nigromaculata has not been recorded from the western part of the Gulf. This species was common among the oysters of the Port Isabel area. Nereis pelagica occidentalis Hartman. This polychaete was common among oyster clumps as well as in other parts of this area. This bright red worm becomes an active surface swimmer at night, especially during the summer months, and will come to a bright light at night. They are readily taken as food by small fish. PHYLUM ARTHROPODA CLASS CRUST ACEA ÜRDER CoPEPODA Ali species not otherwise noted were taken from Brazos Santiago Pass. Acartia lilljeborgi Giesbrecht. Acartia tonsa Dana. Most abundant of all copepod species, found at all times and at all stations, withstands high salinities and has been found in almost fresh water. Anomalocera ornata Sutcliffe. Calanopia americana Dahl. Centropages furcatus (Dana). Clausocalanus furcatus (Brady'). Eucalanus pileatus Giesbrecht. Labidocera scotti Giesbrecht. Labidocera aestiva Wheeler. Macrostella sp. Rare throughout the area. Metis holothuriae (Edwards) =(M. jousseaumei Richards). Most common at station 25 in summer months. Oithona brevicornis Giesbrecht. Rare throughout the area. Paracalanus aculeatus Giesbrecht. Paracalanus crassirastris Dahl. Paracalanus parvus (Claus). Pontellopsis villosa Brady. Temora stylifera (Dana). An Ecologica/, Survey o/ the Lower Laguna Madre Temora turbinata (Dana). Tisbe sp. T ortanus sp. ÜRDER CIRRIPEDIA Bdanus eburneus Gould. The "ivory barnacle" was found wherever there was a place for attachment. Balanus amphitrite Darwin. More common in lower salinity waters near Brazos Santiago Pass. Lepas pectinata Spengler. Found on floating sargassum weed. ÜRDER ISOPODA Nerocila acuminata Schioedte and Meinert. Parasitic in the mouths of croakers (Mic· ropogon sp.). Probopyrus pandalicola Packard. Parasitic on gills of Pdaemonetes intermedius. ÜRDER AMPHIPODA Amphipods were very common throughout the entire area, but little work has been done with them at this time. They were found among dead and living grasses, and algae, as well as among barnacles and oyster clumps. Elasmopus sp. Common among green algae. Grubia compta (Smith). Common among green algae. Caprella sp. Rare in plankton samples near Port Isabel, a different species common on the brown algae of Brazos Santiago jetties. ÜRDER DECAPODA Penaeus setiferus (Linnaeus). The white shrimp was rare in most areas of this region, but a large population was present from June to September in a shallow, almost en· closed, water area immediately north of the junction of the Arroyo Colorado and the lntracoastal Canal, immediately west of the spoil banks at lntracoastal Canal marker 324. South Bay and the Arroyo Colorado were frequently used as a sum· mer nursery grounds for this species of shrimp. Penaeus aztecus lves. The brown shrimp was present throughout the entire area at all times, but was very scarce during winter months. The middle area was an important nursery grounds. Although it does not reach sufficient size for table use in this area, this shrimp provides a basic food for the spotted trout and the southern flounder. Penaeus duorarum Burkenroad. The pink shrimp was found in the summer months, interspersed with the brown shrimp in the Port Isabel area, particularly near the Brownsville Ship Channel. Apparently it cannot tolerate as high a salinity as P. aztecus and has not been found north of Three lslands. Palaemonetes intermedius (Holthuis). Very common throughout the area, found among the green algae of the Arroyo and among shoal grass in the Laguna, tolerant of both high and low salinities and temperatures. One female specimen, which was doubly infected with Probopyrus pandalicol.a Packard ( one in each gill chamher), was taken, apparently a rarity. Crangon heterochaelis ( Say) . The pistol shrimp w as found among the oyster elumps of Port Isabel and was cornmon along the south and west shore of Port Isabel Bay. This shrimp appeared to be abundant on the shallow flats in the Three lslands area, as evidenced by its presence in the stomachs of the redfish Sciaenops ocellatus ( Linnaeus) taken there. Tozeuma carolinensis Kingsley. Found in Port Isabel Bay during the summer months. Pagurus sp. Not numerous, but found near the Brownsville Ship Channel. Hepatus epheliticus (Linnaeus). Scarce, a few strays near the jetties at Port Isabel. Calappa fiammea (Herbst). Also rare, but occasionally entered the approach to the Brazos Santiago jetties. Callinectes sapidus Rathbun. Very common in the juvenile stages during the spring months. Adults were present throughout the entire area during the summer, with males present ali year. Callinectes danae Smith. The Gulf crab was the predominant portunid in the vicinity of Brazos Santiago Pass and in South Bay. Neopanope texana (Stimpson). Mud crab, very common in the vicinity of Three lslands. Uca sp. Fiddler crabs were cornmon in the low-lying areas near the bay. Pinnotheres ostreum Say. The oyster crab was common near Port Isabel. The female was found living commensally in commercial oysters in the area. Mewporhaphis sp. Spider crabs were taken periodically by trawl near Brazos Santiago jetties. Libinia sp. As in the species above. ÜRDER STOMATOPODA Squill.a sp. Mantis shrimp were taken in trawl drags in the Port Isabel area during the summer months. PHYLUM MoLLuscA Many species of molluscs were represented in the area only by the presence of their dead shells. Where the live animals of these species were not found, they are not listed here. Other species which are not listed are those Gulf forms which were accidentally and temporarily introduced into the hay area. Pulley (1952) and Abbott (1954) were valuable in the identification of these species. CLASS AMPHINEURA ÜRDER PoLYPLACOPHORA Severa! chitons have been collected from the Port Isabel area, but most have not yet been identified. Chaetopleura apiculata (Say). Common among the experimental oyster reefs of Port Isabel Bay. CLASS PELECYPODA Brachúlontes exustus Linnaeus. Common on oyster clumps in the Port Isabel area. Aequipecten irradians amplicostatus Dall. Very common from Three lslands south in the spring months, apparently migratory. Anomia simplex d'Orbigny. Common on inner surfaces of dead oyster shells. Crassostrea virginica (Gmelin). Common in South Bay and commercially harvested there, also present in quantities at Queen lsabella Causeway, Port Isabel. There were deposits in other scattered areas in the Port Isabel area. This population may be a new physiological race, as it not only tolerated, but spawned and achieved rapid growth, in salinities in excess of 40 roo. Special attention was given to the commercial oyster population centered in South Bay, the only sizable concentration of oysters south of Corpus Christi, and unique in many ways. South Bay was almost totally lacking in water circulation. Water depth averaged 18 inches and was usually very turhid. The bottom was of soft mud to which other layers were added yearly by nearby dredging. Water temperatures ranged to both extremes, and salinities remained steady at 32 to 42 %o· In spite of these seemingly adverse conditions, limited oyster production has con­tinued for 25 years. In spite of the limited cultch, spatfall seemed to he more than adequate. Spawning, while occurring daily in spring and fall, continued throughout the year, as shown by the presence of ali sizes of spat and seed oysters at any given time. A percentage of the total adult population were in an edible condition throughout the year, as indicated by the year-round commercial harvest. Most landings occurred in summer when commercial oyster harvest was prohibited by law in the main oyster producing areas of the state. The study of South Bay oysters has given rise to a developmental project now under­way. In April of 1958, six quarter-acre oyster reefs were built in Port Isabel Bay (Fig. 4). Each reef was made by depositing a six-inch deep layer of mud shell, using 300 cubic yards for each reef. Three of these reefs were then seeded, each with 200 bushels of South Bay seed oysters (Reefs 2, 5, and 6). The purpose of the experiment was to determine whether these oysters would do as well in the seemingly more favorable environment of Port Isabel Bay as in South Bay. The experimental reef areas were vastly different from South Bay in type of bottom, water depth, temperature extremes, siltation, and water circulation. Salinity was essen­tially· the same in both areas. Results of this study are far from complete. A sudden prolonged reduction in salinity in the area in October and November of 1958 caused high mortality among both seed oysters and spat. Sorne seed oysters managed to survive the reduced salinity, showing a salinity tolerance of at least 1.4 %o to 42.0 %o since planting. Y oung oysters of ali lengths from 4 to 90 mm were present at all times, indicating a somewhat continuous spawning. Growth to 90 mm on spat collectors has been attained in one year on several reefs during 1958. At the present time, these reefs are most valuable as fishing reefs; their futu re as producers of commercial oysters is in doubt. Ostrea equestris Say. Very common in the Port Isabel areas, especially near the jetties and along the base of the causeway. The main spatfall of the horse or gulf oyster, Ostrea equestris, occurred in April and May, 1958. This oyster was more abundant on the reefs nearest Brazos Santiago Pass; it was almost unknown in South Bay. Seeded reefs contained a higher percentage of commercial oysters ( Crassostrea) than the unseeded reefs at this time. Mortality occurring during a period of decreased salinity was greater among the horse oysters than among the commercial oysters. Polymesoda fioridana Conrad. Found throughout the hay area but not abundant. Laevicardium mortoni Conrad. Present over much of the hay bottom, fairly common. Anomalocardia cuneimeris Conrad. Found from Three lslands north to the land cut. Chione cancellata Linnaeus. Common during spring and summer months from Three lslands south to the Brownsville Ship Channel. Mercenaria campechiensis Gmelin. A few specimens remain in South Bay. This species was harvested commercially' befare the dumping of spoil far the Brownsville Ship Channel dredging. Other live specimens have been faund in the vicinity of ex­perimental oyster reef 4. Tagelus gibbus (Spengler). Found along the Brownsville Ship Channel. Ensis minor Dall. Fresh dead shells common throughout the area. Mulinia lateralis (Say). Found from Three lslands north. Used as faod by the black drum along with P. fioridana, L. mortoni, and A. cuneimeris. No large deposits of any of these have been faund to date. Pholas ( Barnea) costata Linnaeus. The angelwings were common in a few areas at Port Isabel. Congeria (Mytilopsis) sallei Recluz. Very abundant far a short time only during the summer of 1956 in the Arroyo Colorado, absent befare and since. CLASS GASTROPODA ÜRDER PROSOBRANCHIA Neritina virgínea (Linnaéus). Common among shoal grass on south shore of Port Isabel Bay. Littorina ziczac Gmelin. Very common on the jetties at Brazos Santiago Pass. Littorina nebulosa Lamarck. The angulate periwinkle was faund on pilings near Brazos Santiago Pass and in the Port Isabel basin. Littorina irrorata Say. The marsh periwinkle was found adhering to grass and reeds near Port Isabel and along the Brownsville Ship Channel. Cerithium variabile C. B. Adams. Cerithidea pliculosa Menke. Rare, south of Three Islands. Epitonium sp. Crepidula plana Say. Common in the Port Isabel area. Murex fulvescens Sowerby. Thais haemostoma fioridana Conrad. Very common on the Brazos Santiago jetties. Anachis avara semiplicata Stearns. Nassarius vibex Say. Common in Port Isabel Bay. Pleuroploca gigantea (Kiener). Found under Queen Isabella Causeway. ÜRDER ÜPISTHOBRANCHIA SusoRDER TECTIBRANCHIA Tectibranchs are fairly common in the summer months in the Port Isabel area. In addition to those listed here, three other species have been collected but not yet identi­fied. Bulla occidentalis C. B. Adams. Rare in Port Isabel Bay. Bursatella leachi pleii (Rang). The ragged sea hare, a blue green in color, was taken at Station 15 during the summer months by trawl, a new record from Texas. An Ecological Survey o/ the Lower Laguna Madre Aplysia (Tethys) willcoxi Heilprin. The mottled sea hare was common at Port Isabel, a new record from Texas. Aplysia (Tethys) dactylomela Rang. Larger than A. willcoxi and with black rings, com­mon. Aplysia (Tethys) fioridensis Pilsbry. Uniform purple black color, rare with only one specimen taken until the summer of 1959 when over 100 specimens were sighted in Brazos Santiago Pass. ÜRDER PULMONATA Siphonaria lineolata d'Orbigny. Common on the Brazos Santiago jetties. CLASS CEPHALOPODA ÜRDER DECAPODA Loligo brevis Blainville. Fairly common near the Queen Isabella Causeway during the summer months and rare in South Bay during the winter months. PHYLUM EcHINODERMATA CLASS ÜPHIUROIDEA Severa] unidentified species are common on the oyster clumps of Port Isabel. CLASS EcHINOIDEA Arbacia punctulata (Lamarck). Found south of Queen Isabella Causeway, but not common. Lytechinus variegatus (Lamarck). Common at Station 15 in late spring and early summer. Mellita quinquesperforata (Leske). A few specimens taken just inside the Brazos Santi­ago jetties. The young were very common just past the surf on the Gulf beach in June. CLASS CRINOIDEA Crinoid material was taken from under the Queen Isabella Causeway, but no identifi­cations have been attempted as yet. CLASs HoLoTHUROIDEA Thyonella sabanillensis (Deichmann). Severa] specimens were taken adjacent to Browns­ville Ship Channel just inside jetties. ÜRDER APODA Synaptula hydriformis (LeSueur). Very common east of Intracoastal Canal from Queen Isabella Causeway to Three Islands in summer. PHYLUM EcTOPROCTA CLASS GYMNOLAEMATA Membranipora tuberculata (Bosc). Common on sargassum weed near Port Isabel. PHYLUM CHORDATA ÜRDER SELACHII Sharks were very common at the end of the Brazos Santiago j etties and along the Gulf beach including the Hammerhead, Sphyma zygaena (Linnaeus) , Bonnethead, Sphyrna tiburo (Linnaeus) , and the sand shark Carcharhinus sp. Sharks were seldom seen or caught inside the pass. ÜRDER BATOIDEI Pristis sp. The sawfish has been reported at Port Isabel, but none were taken in the survey work. Raja sp. Oystermen in South Bay report skates, but none were taken in the survey. Dasyatis sabina (Le Sueur). The stingaree was common in South Bay, at the base of the Brazos Santiago jetties, and north to the mouth of the Arroyo Colorado, but rare from there north. Aetobatus narinari (Euphrasen). Two specimens were seen near the Queen lsabella Causeway, not common. Rhinoptera bonasus (Mitchill). Several schools were seen in the lntracoastal Canal near Green Island apparently migrating. Severa! specimens were reported caught near Three lslands on trot lines, not common. ÜRDER LEPISOSTEIDA Lepisosteus productus Cope. Spotted gar. Lepisosteus spatula (Lacépede). Alligator gar as well as spotted gar were common in the brackish and fresh waters of the area, such as the Arroyo Colorado and floodway systems. In times of low salinity, they entered the hay for a period. ÜRDER NEMATOGNATHI Bagre marinus {Mitchill). The gafftopsail catfish was taken occasionally in the Port Isabel area but was not common. Gal,eichthys felis {Linnaeus) the sea catfish (hardhead) was very common throughout the area, especially in the deeper waters of the channels. Male catfish carrying eggs ready for hatching were found at Station 13 on June 22, 1954. ÜRDER JSOSPONDYLI Tarpon atlanticus {Cuvier and Valenciennes). The tarpon was a popular sports fish in the lower Port Isabel Bay area, as well as in the Brazos Santiago Pass. lt was common during the summer months north to Three lslands and in the Arroyo Colorado. Elops saurus Linnaeus. The tenpounder was fairly common, especially in waters of lower salinity'. Dorosoma cepedianum (Le Sueur). The gizzard shad was present in the Arroyo Colorado and North Floodway, rare elsewhere. Brevoortia gunteri (Hildebrand) . The hay menhaden was fairly common in the entire hay area. An Ecological Survey o/ the Lower Laguna Madre Brevoortia patronus Goode. A few specimens of the Gulf menhaden were taken in the Port Isabel area as far north as Three lslands. Both species used the Arroyo Colo­rado as nursery grounds. Anchoviella sp. Very common from Three lslands north to the landlock, and very abun­dant during winter months, it was the most plentiful bait fish in the hay during December and J anuary. ÜRDER INIOMI Synodus foetens (Linnaeus). A few specimens were taken near the Brazos Santiago jetties, not common. Fundulus grandis (Baird and Girard). Fundulus pulvereus (Evermann). Cyprinodon variegatus Lacépede. Ali three were common in the shallow fresh and hrack­ish waters of the area, North Floodway and Laguna Atascosa. ÜRDER SYNENTOGNATHI Strongylura marina (Walbaum). The needlefish was present throughout the area but much more common in the deeper water of the Intracoastal Canal during the sum­mer months. ÜRDER SOLENICHTHYES Syngnathus sp. Pipefish were very common in trawl drags throughout the hay area. Hippocampus sp. An occasional adult sea horse was taken at Station 15. Young were common in the manatee grass in South Bay. D1v1s10N AcANTHOPTERYGII Menidia beryllina peninsulae (Goode and Bean). The tidewater silverside was common in the area but more abundant in summer in the less saline waters. It replaced the anchovy of more saline waters. Mugil curema Cuvier and Valenciennes. Mugil cephalus Linnaeus. Both the striped and white mullet were common throughout the area, particularly in the Arroyo Colorado and the Intracoastal Canal. Juvenile forms were found in the Arroyo in December and January. Polydactylus octonemus Girard. The eight-fingered threadfin was present but not com­mon and was most abundant along the Brownsville Ship Channel. Scomberomorus maculatus (Mitchill) . The Spanish mackerel was common in the Gulf waters adjacent to shore during the spring and summer months, and a few indi­viduals occasionally entered the hay area. Scomberomorus cavalla (Cuvier and Valenciennes). The king mackerel usually was found slightly farther offshore than the Spanish mackerel, but clear water in close to shore brought these fish in almost to the beach. Sorne specimens have been taken from the jetties but notas often as the Spanish mackerel. Trichiurus lepturus Linnaeus. The cutlass fish was a common resident of the lntracoastal canal during the summer from Port Isabel to the mouth of the Arroyo. Caranx hippos (Linnaeus). The adult common jack, an offshore species, has not been taken in the hay, but juveniles of the species were taken near the jetties. Caranx crysos (Mitchill). Hardtail jack were relatively common near the jetties and causeway. Vomer setapinnis (Mitchill). The moonfish was common along the Gulf beach and the jetties. Chloroscombrus chrysurus (Linnaeus). The bumper, which commonly travels with schools of menhaden, was occasionally seen near the jetties. A few specimens entered the hay. Selene vomer (Linnaeus). The lookdown was common along the Gulf beach in the sum­mer months in company with the moonfish. Trachinotus carolinus (Linnaeus). The common pompano was a regular resident of Port Isabel Bay during the spring and summer months, especially from the Queen Isa­bella Causeway northwest to Port Isabel and north to Three lslands and Port Mansfield. Peprilus alepidotus (Linnaeus). The harvestfish was commonly taken by hook from the jetties by sportsfishermen in the spring and early summer. Poronotus triacanthus (Peck) . The butterfish was also common at the jetties and was taken along with the harvestfish. Centropomus undecimal,is (Bloch). The snook, or pike as it is known locally, was com­mon during the warmer months at the mouth of the Rio Grande. In winter it was readily taken by spoons and plugs in the deep waters of the Brownsville Ship Channel. Mycteroperca sp. Epinephelus sp. Severa! species of young grouper not yet identified have been taken by trawl at Station 15 during late spring and early summer. Promicrops itaiara (Lichtenstein). The spotted jewfish was a common resident of the "caves" under the Brazos Santiago jetties as well as in the sunken ships and other submerged wrecks. The young have not been found. Lobotes surinamensis (Bloch). The triple-tail was found in the summer months from the jetties north to Three Islands, usually floating on its side beneath rafts of dead shoal grass, sargassum weed, or floating lumber. Lutjanus sp. Lutjanus apodus (Walbaum). The schoolmaster and other snappers were common at Station 15 from April to July. Haemulon sp. Orthopristis chrysopterus (Linnaeus). The pigfish, highly prized as bait for large spotted trout, was not too common in the area. Most specimens have been taken in the Port Isabel area. Lagodon rhomboides (Linnaeus). The pinfish was very common throughout the entire area. lt was tolerant of a wide range of salinity and temperature. In this area, the pinperch constituted a large percentage of the diet of the spotted trout and was used as live bait for trot lines. Archosargus probatocephal,us (Walbaum). The sheepshead was quite common in the Port Isabel area, especially under piers and docks, although large schools have been seen in the open hay as far north as Port Mansfield. In January, large schools of sheepshead were common in Redfish Bay, and the young (30-50 mm) were present at Three Islands. Eucinostromus gul.a (Cuvier and V alenciennes) . Eucinostromus cali/orniensis (Gil!). Both the common and Gill's mojarra were abundant in the area, but no attempt was made to separate species after initial identification. Cynoscion arenarius Ginsburg. Cynoscion nothus (Holbrook). Both species of sand trout have been taken at Port Isabel near the approaches to the jetties. Neither was common in the area and seldom were they found far into the hay proper. Cynoscion nebulosus (Cuvier and Valenciennes). The spotted seatrout was common to the entire area and sought after by both the sports and commercial fishermen. They were present throughout the year and were taken on trot lines baited with live perch, piggies, with plastic, by spoons, plugs, or shrimp. Juvenile trout were found among beds of dense shoal grass in many areas of the hay. Nursery grounds were extensive throughout the area except in Port Isabel Bay and in South Bay. Adult trout were found throughout the hay in the warmer months but were confined to the deeper waters of the hay and channels during the coldest months. Many trout were taken with spoons and live shrimp from the jetties or Gulf surf during winter months, indicating a migration to the gulf of sorne of the trout popultaion during the coldest weather. Tagging results indicate that trout which wintered in the Arroyo Colo­rado spent the summer months in the grassy areas along the intracoastal canal from Three Islands to the Cameron-Willacy County line. Trout in the Redfish Bay area were believed to follow the brown shrimp migration north to the land cut in early spring. Prior to 1955, juvenile brown shrimp were the most important food ítem in the diet of smaller trout ( 1 to 3 pounds) . Sin ce that time, however, the use of the swarming nocturnal polychaete, Nereis pelagica occidental,is Hartman as food by these trout has increased considerably, especially' along the intracoastal canal from Port Mansfield to Three Islands. This shift in food preference and the resulting change from daytime to night time feeding has resulted in decreased daytime trout catches, since it appears that this trout population does not feed with equal vigor both day and night. Experimental net catches made in the mornings revealed a sizable trout population with stomachs full of polychaete worms. This change in feeding time was quickly noted by the sports and commercial fishermen, who began fishing with live shrimp in the channels at night under batteries of lights. These lights attracted large numbers of shrimp, small fish, crahs, and worms which, in turn, attracted the trout. This method has become the most reliable way of catching large numbers of trout in this area. Large sow trout, ranging from 8 to 14 pounds, were common to the area hut did not appear on the sports stringer in sufficient numbers to indicate their presence in the area. Live shrimp was the most popular trout bait in the region, but did not hring in large fish for trout over eight pounds were fish eaters, feeding primarily on mullet, skipjack, pinperch, piggies, and other trout. lndications of the large sow trout population in the area were given by experimental netting, illegal net landings, fish kills, and trot line landings when fish were used for hait. Bairdella chrysura (Lacépede). The silver perch, locally called "yellow tail" was com­ mon in the Arroyo Colorado and the Port Mansfield channel. Both young and adult have been taken adjacent to the Brownsville Ship Channel in late winter. Stellifer lanceolatus (Holbrook). The star drum was common in the Gulf in three to five fathoms but seldom entered the hay area. Sciaenops ocellatus (Linnaeus) the channel bass (redfish) was also common to the entire area and was the fish most sought in the area by both sports and commercial fishermen. (Simmon & Breuer, 1962). While the Gulf surf is thought to be the spawning grounds of the mature redfish, no eggs or larval redfish have been taken either from the Gulf beach or from the passes, even though mature redfish were common in the bays near the passes in late fall and in the Gulf surf in winter. The hay nursery grounds of the juvenile redfish extend along the hay side of Padre lsland from the Queen lsabella Causeway north for a distance of twelve miles. Red­fish of less than one year ( 7 to 10 in ches) were common in the Arroyo Colorado, Cayo Atascosa, and the lntracoastal Canal near Green Island during the summer months.Year class 1 to 111 were abundant throughout the year on the flats, princi­pally along the hay shore of Padre lsland. Sorne year class IV and older fish entered the hay in late fall and apparently engaged in heavy feeding before returning to the Gulf to spawn. leiostomus xanthurus (Lacépede) the spot croaker is found throughout the area but not in large numbers. The ova and larvae are not known to the area, and specimens of over 8 inches are rare. Micropogon undulatus (Linnaeus) The golden croaker was very common to the region. Juveniles appeared at the passes and in the Gulf surf in December and January. By February the entire hay was filled with 20 to 40 mm croaker. Specimens of five to eight inches were plentiful in the channels during the summer. Large schools of adult croaker have been reported in the lntracoastal Canal but have not been ob­served. A few 35 to 40 mm specimens have been taken near the passes in January and sorne with roe south of East Channel in October. Spawning apparently occurs in the Gulf during late fall (Pearson, 1929). Menticirrhus littoralis (Holbrook). The whiting or "ground mullet" was common in the surf of Padre Island but seldom entered the hay area. Pogonias cromis (Linnaeus). The black drum was very common throughout the hay area, especially from Three Islands north. (Simmons & Breuer, 1962) Juvenile drum have been found in the Arroyo Colorado, Cayo Atascosa, and in the shallow sloughs west of Port Isabel in the late spring and early summer months. Drum of from 7.5 to 22.5 mm known as "butterfly drum,'' were common in the lntracoastal Canal from Three Islands to Port Mansfield during the summer months. Adults were numerous on the flats throughout the year, often traveling in large schools. Severe cold weather caused them to move to the channels. lnflux of fresh water caused them to migrate up the Arroyo Colorado and the floodways. Large drum were common in the surf during the winter months. Not usually sought by sports fishermen, these large drum are of marketable value to the commercial men. The Game and Fish Commission, operating under authority of the Legislature, has been attempting to reduce an excessive black drum population in this area by authorizing contract drum netting in Cameron and Willacy counties during certain An Ecological Surver o/ the Lower Laguna Madre winter months. This netting alone has resulted in the harvest of over 750,000 pounds in 1959-60 and over 1,000,000 pounds in 1960-61. Abudefduf saxatilis (Linnaeus). The sergeant-major is a resident of the Brazos Santiago jetties. Two specimens of parrot fish were taken at Station 15 during May and June 1956 but not yet identified. Chaetodipterus faber (Broussonet). Spade fish of ali sizes are common at the Brazos Santiago jetties. Spheroides sp. Small specimens of a species yet undetermined are common at Port Isa­bel. Chilomycterus schoepfi (Walbaum). The spiny boxfish is common from the Queen Isa· bella Causeway north to Three lslands during late spring and early summer. Scorpaena sp. Common at Station 15. Prionotus sp. A few sea robins were taken near the Queen lsabella Causeway but were not common. Dormitator maculatus (Bloch). Two sleepers were taken in the Arroyo Colorado during periods of excessive fresh water. Erotelis smaragdus (Cuvier and Valenciennes). The emerald goby has been taken at Station 15 but is not common. Astroscopus r·graecum (Cuvier and Valenciennes). Two specimens were taken each at the mouth of the Arroyo and at Station 15, not common. Opsanus beta (Goode and Bean). The oyster dog or toadfish was common over much of the area, especially at the mouth of the Arroyo and at Station 15. Citharichthrs spüopterus Gunther. The spot-finned whiff was common in the trawl sam­ples in and adjacent to the Brazos Santiago channel. Ancylopsetta quadrocellata Gill. The ocellated fluke was fairly common from the ap· proach to the jetties to Port Isabel. Paralichthrs albiguttus Jordan & Gilbert. The Gulf fluke was a resident of the open Gulf, where it was taken in quantity by the Gulf shrimp trawls. A few specimens enter the hay and are common near Port Isabel. Paralichthrs lethostigma Jordan and Gilbert. The southern fluke is the commercial flounder of the area and was found throughout the entire area. Most common dur­ing the warmer months, sorne mature individuals remained in the area throughout the winter. Specimens from 35 to 50 mm were taken in December. Symphrus plagiusa (Linnaeus). The tonguefish was fairly common in trawl drags ad· jacent to the approach to the Brazos Santiago channel. Young of 20 to 30 mm have been taken in January near Port Mansfield. Histrio histrio (Linnaeus). The sargassum fish was common to the area near Port Isabel, where it was found among its usual habitat, the sargassum weed. Ogcocephalus radiatus (Mitchill). Two specimens have been taken at Station 15, not common. Fish Mortality Abnormal mortalities of fish in the lower Laguna Madre were caused by pollution, sudden drops in water temperature, sudden influxes of fresh water, and by red tide. Pollution was not a serious problem in the area. Sorne minor fish kills in municipal or industrial areas have occurred (Port Brownsville and Port Harlingen) but little orno eflect was noted in the Laguna Madre proper. Sudden drops in water temperature during excessively cold and prolonged northers have done catastrophic damage to marine life in this area in the past and undoubtedly will in the future. The "freeze" of February 1951 caused great damage to fish, and this was reflected in sports and commercial landings for the next three years. No significant fish kills dueto "freezes" occurred from 1951to1959. During periods of heavy rains or river flooding, a sudden drop in salinity often killed fish in the Arroyo Colorado. Flounder, trout, catfish, hardhead catfish, blue crabs, and shad were the principal victims, but the total number was minor as compared with the total population of these species in the hay proper is such that the damage is negligible. On and about September 10, 1955, a heavy concentration of Gymnodinium brevis in the Gulf surf caused a "red tide" kili on the island beach from the mouth of the Río Grande to a point sorne 15 miles north of Brazos Santiago Pass. Samples taken by the U.S. Fish and Wildlife Service showed 50 to 500 individuals of G. brevis per mi of wa· ter. Kill was moderately light, and only scrap fish were affected. Sixteen days later, an· other kili was reported in the same area. Found dead were bull and rat reds, pike, trout, drum, and pompano, along with many scrap fish. These two "red tide" kills coincided with earlier rains, increased flow of the Río Grande, and warm temperatures. No red tide organisms were found in the hay samples. Kili in both cases was considered light. Since the dredging of the Intracoastal Canal in 1948, fish kills due to hypersalinity have not occurred. Effects of Dredging in South Bay South Bay (Fig. 4), the southernmost hay area, líes between the Brownsville Ship Channel and the Río Grande. Major ecological changes have taken place there in the past twenty-five years due to spoil from dredging. The Brownsville Ship Channel was completed to a depth of 28 feet in 1938, and much of the resulting spoil from the east end of the channel was placed in a linc along the north end of South Bay. This and sub· sequent redredgings effectively closed the entrance to South Bay with the exception of a narrow, shallow inlet. This spoil deposition prevented the natural water circulation from the Gulf, through South Bay and Boca Chica Pass into the Laguna Madre. Boca Chica Pass was dependent on the strong annual northers to push large volumes of water from the Laguna Madre, through South Bay, and out through the pass to keep it scoured. As a result of the spoil deposition, Boca Chica Pass filled in rapidly and closed finally in 1945. Since that time, circulation in South Bay has hecome non-existent, and average water depth has decreased from 4 feet to an average of less than 18 inches, and each subsequent re-dredging of the channel reduces the average depth even more. The layers of dead oyster shell correspond to the layers of deposited spoil and indicate that much of the South Bay oyster population was destroyed with each dredging opera· tion. Commercial oystermen reported decreased harvest following dredging operations. Commercial and sports fishermen report fishing in South Bay has heen reduced to in· significance. The pumping of mud into the hay was more rapid than the ability of the vegetation to cover it, resulting locally in water of very high turhidity. A series of bars has been built up across the hay which retards circulation and prevents boat travel in the hay. The hay bottom is mostly of soft mud. Port Mansfield Pass Since the initial completion of the East Channel, pass, and jetties in October of 1957, several notable changes have occurred in the ecology of the adjacent hay area. The crop of class O year redfish throughout the lower Laguna Madre in the summer of 1958 was notably greater than in many years past. This increase was noted in com­mercial landings at Port Mansfield, which showed a substantial increase in year class 1 plus during the summer and fall of 1959. There was another excellent crop of class O redfish in summer of 1959. These two consecutive yearly increases in young redfish pro· duction coincided with the first two years after the opening of Port Mansfield pass. Prior to the opening of the pass, the summer juvenile brown shrimp populations of the Lower Laguna Madre seldom extended north farther than Station 21, as shown by monthly trawl samples made throughout the period. Since the opening of the pass, how· ever, brown shrimp have been taken in quantity at ali stations in Redfish Bay, and sizable concentrations were noted in April of 1959 in Redfish Bay along the Padre Island shore from East Pass to the land cut. The landings of flounder by both sports and commercial fishermen have increased manyfold since the opening of the Pass. lncreased commercial landings are reported by Port Isabel and Port Mansfield fish dealers, and increased sport catches were reported by bait stand operators and noted by personal observations. Flounder, which previously had seldom ventured north of the Cameron-Willacy County line, are now abundant north to the land cut. Vegetation, both shoal and widgeon grass, has increased in the area, both in range and in stand. This was shown by comparing vegetative mappings by the author in 1955 and 1957 with mappings made by Mr. James Pipkin, Wildlife Biologist for the Texas Game and Fish Commission in 1961. Pig fish, Ortlwpristis chrysopterus, the most preferred food of the sow trout, have ap· peared throughout the area in large amounts. Prior to the opening of the pass, the piggy was rare in the area and taken only as scattered individuals. Prior to 1957, adult and juvenile pinperch, the most important bait fish of the area, entered the Laguna Madre through Brazos Santiago Pass in late J anuary and early February and migrated steadily northward. lt was late April and early May before this population reached the extreme north end of Redfish Bay as evidenced by extensive trawl sampling. Since 1957, pinperch populations return to the area as early as late January, providing food for the trout at least three months earlier than before. In addition, the fall migration of pinperch to the Gulf was delayed at least a month so that a sizable pinperch population existed in Redfish Bay for 10 to 11 months (Jan· uary to November) as compared to six to seven months (May to November) prior to the opening of the pass. It has also been noted from trawl samples that juvenile trout have been located in abundance on the established grass beds which have increased in stand since the open· ing of the pass. This has occurred in areas where juvenile trout were not recorded prior to 1957. Summary l. Hydrographic data and annotated comments on species are presented for the lower Laguna Madre, an elongated lagoon seventy-four miles in length and three to eight miles in width in Cameron, Willacy, and Kenedy Counties of South Texas, separated from the Gulf of Mexico by Padre and Brazos lslands. Water depths range from twelve feet to a few inches, and the total water area is in excess of 150,000 acres. 2. This hay is noted for a high production of spotted trout, redfish, and black drum. 3. Fish kills are caused by pollution, "red tide" influxes of fresh water, and by ex­treme cold temperatures. 4. Planktonic species forms are most varied near the passes and during the summer months. 5. Brown algae are very common in Port Isabel Bay especially Gracüaria blodgetti Harvey. 6. Five species of spermatophytes are present in the area with Diplanthera wrightii Aschers most widely distrihuted. 7. The sponges and coelenterates are largely confined to the area adjacent to the Gulf. 8. Ctenophores are common throughout the area, especially in the winter months, with Beroe ovata Chamissa and Cypenhardt the most common species. 9. Annelids are present all over the area, inhabiting the oyster beds, and sand or mud bottom. Several forms are important to the diet of game fish. 10. Of the many species of copepoals of marine fisheries biology. Pub!. lnst. Mar. Sci. Univ. Tex. 2(1): 181-'212. Carlgren, Oskar, and Joel W. Hedgpeth. 1952. Actiniaria, Zoantharia and Ceriantharia from shallow water in the northwestern Gulf of Mexico. Pub!. lnst. Mar. Sci. Univ. Tex. 2(2): '143-172. Collier, Albert, and Joel W. Hedgpeth. 1950. An introduction to the hydrography of the tidal waters of Texas. Pub!. lnst. Mar. 'Sci. Univ. Tex. 1 (2) : 125-194. Freese, Leonard Roy. 1952. Marine diatoms of the Rockport, Texas, bay area. Tex. J. Sci., '4(3): 351-386. Gunter, Gordon. 1945. Studies on marine fishes of Texas. Pub!. lnst. Mar. 'Sci. Univ. Tex. 1(1): 1-190. ----. 1950. Seasonal population changes and distributions as related to salinity of certain invertebrates of the Texas coast, including the commercial shrimp. Pub!. lnst. Marine Sci. Univ. Tex. 1 ('2) : 7-51. Hartman, Oiga. 1951. The littoral marine annelids of the Gulf of Mexico. Pub!. Inst. Mar. Sci. Univ. Tex. 2('1'): 7-"125. Hedgpeth, Joel W. 1950. Notes on the marine invertebrate fauna of salt flat areas in the Aransas National Wildlife Refuge, Texas. Pub!. lnst. Mar. Sci. Univ. Tex. 1 (2): 103-119. ----. 1953. An introduction to the zoogeography of the north-western Gulf of Mexico with reference to the invertebrate fauna. Pub!. lnst. Mar. Sci. Univ. Tex. 3(1): 109-'2'24. Humm, Harold J., and R. L. Caylor. 1957. The summer marine flora of Mississippi Sound. Pub!. lnst. Mar. 'Sci. Univ. Tex. 4(2): 2'28-264. Ladd, Harry S. 1951. Brackish-water and marine assemblages of the Texas Coast with special ref­erence to mollusks. Pub!. lnsL Mar. Sci. Univ. Tex. 2 (1) : 129-162. Parker, Robert H. 1959. Macro-invertebrate assemblages of central Texas coastal bays and Laguna Madre. Amer. Ass. Petrol. Geol. 43(9): 2100-2'166. Pearson, John G. '1929. Natural history and conservation of the redfish and other Sciaenids of the Texas coast. Bull. U. S. Bur. Fish. 44(1928): 1'29-21'4. Pulley, T. E. 19512. An illustrated checklist of the marine mollusks of Texas. Tex. J. Sci. 4(2·): 167-199. Rusnak, G. A. 1960. Sediments of Laguna Madre, Texas, p. 1'53-196. In Shepard, F. P., F. B. Phleger, and T. H. van Andel; Recent Sediments, Northwest Gulf of Mexico. Amer. Ass. Petrol. Geol., Tulsa. 394 p. Shepard, Francis P., and Gene A. Rusnak. 195'7. Texas hay sediments. Pub!. Inst. Mar. Sci. Univ. Tex. 4(2) : 5-:13. Simmons, Ernest G. '19S7. An ecological survey of the upper Laguna Madre of Texas. Pub!. Inst. Mar. Sci. Univ. Tex. 4(2): 156-200. Simmons, Ernest G., and Joseph P. Breuer. 1962. A study of redfish, Sciaenops ocellata Linnaeus, and black drum, Pogonias cromis Linnaeus. Pub!. lnst. Mar. Sci . Univ. Tex. 8: 184-211. U. S. Dept. of Interior, Fish and Wildlife Service. 195'4. Gulf of Mexico, its origin, waters and marine life. Fish. Bull., U. S. 55: 1-604. Whitten, H. L., Hilda F. Rosene and J. W. Hedgpeth. 1950. The invertebrate fauna of Texas coast jetties; a preliminary survey. Pub!. lnsL Mar. Sci. Univ. Tex. 1 (2): 53-87. A Study of Redfish, Sciaenops ocellata Linnaeus and Black Drum, Pogonias cromis Linnaeus1 ERNEST G. S1MMONS AND JosEPH P. BREUER Marine Laboratory, Texas Game and Fish Commission, Rockport, Texas Abstract Data on redfish, Sciaenops ocellata, and the black drurn, Pogonias cromis, are presented from 1949 to 1959. Redfish spawn in the Gulf of Mexico during fall and winter months but the exact site of this spawning is uncertain. Y oung fish rnove through passes into nursery grounds into the bays where they remain from six months to three or four years. Growth is rapid and standard lengths of 320, 530 and about 700 mm. are reached during the first three years. Spawning norrnally occurs al the end of the third or fourth year when the fish are 700-800 mm long, but ripe fish as small as 450 mm. have been found. Although the species is euryhaline, individuals are most often found at salinity of '20-40 %0• Extreme temperatures of 3--33º degrees C. are tolerated but sudden drops in water temperature cause rnortality. The food of redfish is primarily crabs, but shrimp and small fish are also consumed. More redfish are found in the bays during spring and fall months than in winter or sumrner, but sorne are present ali year. Migrations are much less extensive than had been supposed and intrabay movement is relatively rare. Sorne schools of redfish are almost perrnanent residents of the Gulf while others rarely leave the bays during the first three or fonr years of life. Black drum spawn in ali of the bays and over any type bottom, as well as in the Gulf near passes. Most spawning takes place in February or March, but there is a prolonged or split season in May or June. Growth is less rapid than that of redfish and standard lengths of about 160, 310, and 415 mm are attained in the first, second, and third years. Tagging results indicate growth of 50 mm per year after the third year. Drum are euryhaline and have been found in salinities from 0-80 %0• At this higher salinity many are blinded or in poor condition, and spawning does not occur. There is a definite temporary movement to fresh water creeks during flood periods. Most movement is random during feeding; food consists primarily of small mollusks although vegetation, small fish, polychaete worms and shrimp are also consumed. Their habit of grubbing for food is detrimental to spawning areas of trout and nursery areas of trout, redfish and shrimp. Parasitic copepods, primarily of the genus Caligus are found on both redfish and drum but are lost when salinity rises above 45 %0• Few isopods have been found on either species. Redfish are sought by sport fisherrnen in the bays and in the Gulf. Drum are less actively sought although there is a substantial tourist fishery for this species. Cree! census figures (Simmons, 1959-60) indica te that over one million pounds of redfish are harvested annually by sports fishermen. Commercial fishing is limited by law but about two million pounds of redfish and drum are harvested each year by various commercial means. ·Catastrophic freezes occurring about every ten years have each destroyed more fish than have been harvested commercially for the past 50 years. Drum are considered to be detrimental to trout and redfish populations since they destroy spawning and nursery grounds, compete for food and space, and are less restricted in spawning requirements. The Laguna Madre tends to become overpopulated with this species very quickly. In an effort to reduce their effects, rough fish perrnits, for drum only, have been issued for certain parts of the Laguna Madre. Introduction The speckled trout, redfish, and black drum, all of the family Scianidae, are three of the most important sport and commercial fish of the Texas region. Guest and Gunter ( 1958) recentiy consolidated scattered data on the speckled trout and squeteagues of the genus Cynoscion. Using the formal of their paper, information on the redfish, Sciaenops ocellata (Linnaeus) and the black drum, Pognias cromis (Linnaeus) is sum· 1 Contribution No. 49 of the Texas Game and Fish Commission Marine Laboratory, Rockport, Texas. marized in this contribution which includes data from recent surveys, unpublished reports, and scattered literature, especially by Pearson (1929), Gunter (1942, 1945, 1946, 1950, 1952), and Miles (1949, 1950, 1951). Areas sampled extended from Pass Cavallo to Port Isabel, Texas (Fig. 1). After separate sections are presented on de­scription and life history of each species, the roles of both species in the sports and commercial fishery are discussed. Redfish DESCRIPTION A full description of the redfish (Sciaenops ocellata) was given in Jordan and Ever­mann (1900). Color was reported as "grayish sil ver, iridescent, often washed with copper red; each scale with a center of dark points, these forming rather obscure, irregular, undulating brown stripes along the row of scales; a jet black ocellated spot about as large as eye at base of caudal above, this sometimes duplicated; the body oc­casionally covered with ocelli." The authors have noted in this study as many as 219 ocelli on an individual fish. The color was normally silvery when the fish had been in Gulf water or in bays with sandy substrate. Those fish captured from turbid water were often coppery, dark, and some­times almost black. Fish normally captured in Texas bays ranged in weight from one to thirty pounds, but large fish were known to exist in the Gulf of Mexico. Very large redfish had blunt heads, often with a lumpy appearance. DISTRIBUTION Redfish range, on the Atlantic coast, as far north as Massachusetts and as far south as southern Florida. Joseph and Yerger (1952) reported that at Alligator Harbor, Florida, they collected redfish adults only in September and that six young were col­lected in March and five more in July. Henry Hildebrand in an oral communication stated that redfish were numberous at Tampico, probably present at Tuxpan, and had not been reported from Vera Cruz. This particular species was found most often in bays or lagoons or in the Gulf surf, but there was one report of a very large school of big redfish at a point 12 miles offshore from Sabine Pass, Texas in 1948 verified by the authors. There have been many unconfirmed reports and one confirmed occurrence from snapper banks near Port Isabel. Planes have sighted many large schools in the Gulf of Mexico. LIFE HISTORY Data concerning sexual maturity and spawning activity have been difficult to obtain as adult redfish normally are found only in inaccessible Gulf water during the spawning period. (Gunter, 1945). Most of the mature stock is derived from the Gulf although Pearson (1929), Miles (1950), Breuer (1957) and Simmons (1957) noted movement of small aggregations of adult fish from the bays to the Gulf. Spawning takes place in late summer (Miles, 1951) and early fall (Pearson, 1929, and Gunter, 1945a, 1950). A few ripe fish were captured in the upper Laguna Madre on January 20, 1960. The presence, of small redfish, 50-125 mm long, in the upper F1G. l. Map of the study showing movements of tagged redfish. A Study of Redfish and Black Drum Laguna Madre in April 1953, 1954, 1955 and 1960 indicates that these fish were spawned in November, December and January. Pearson (1929) noted that maturity is reached at the end of the fourth or fifth year and stated that no redfish under 750 mm were taken in a mature condition. However Gunter (1950) found ripe fish only 425 mm long, Miles (1950) found one gravid female 625 mm long and ripe males 500 mm long and ripe females 550 mm in length were caught in the upper Laguna Madre in January 1960. The exact si te of spawning is uncertain. Pearson ( 1929) observed adult redfish milling about the mouths of passes in October and November and one of the authors observed this activity in October 1950 near Cedar Bayou Pass. In each instance spent adults were found near the beach but no eggs were recovered. Cheesecloth pushnets used in the surf in 1953, 1954, and 1955 took large numbers of other sciaenids but few redfish, and intensive sampling by Hildebrand (personal communication) and by Sim· mons in 1959 and 1960 failed to obtain this species. Pearson (1929) has shown that the youngest redfish are found in the bays just inside passes with larger juveniles moving further into the hay. This indicates spawning takes place in the Gulf or the passes. Mansueti (1961) postulated that planktonic Sciaenops are carried into Chesapeake Bay in September by deep subsurface water currents of high density. Description, Early Devewpment, and Habits o/ Young. Pearson (1929) described young redfish four or five millimeters long as follows: "The yolk sac is present and the dorsal and ventral fin folds are continuous to the caudal fin. The latter is fairly well developed, as are the ventral fins, although the rays of both dorsal and anal are indistinct. Ventrals and pectorals are obscure. One or severa) prominent groups of brown chromatophores or pigment areas are present invariably and these serve, by their approximate location to help identify the young fish at this early stage." During the more recent part of this survey no fish of such small size were located. However, sciaenids 12-15 mm long, captured in the surf, ali appeared to have identical markings and body shape. These, when allowed to grow in aquaria, proved to be mostly golden croaker with only an occasional redfish. A more reliable means of identification is afforded by the relative shape of the caudal and pectoral fins. The pectoral fin of the redfish is more pointed than that of the croaker but the caudal fin is less pointed in the redfish than in the croaker. By the time the fish are 25 mm long, barbels are present on croakers and pigmenta­tion is distinct on redfish. There are 20-50 dark, distinct blotches from the lateral line to the dorsal fin on each side of the trunk and those along the lateral line are somewhat enlarged. Ata length of 42 mm the juvenile redfish is morphologically identical to the adult except for the slightly more pointed caudal fin and the lack of distinct ocelli. (Fig. 2). These distinguishing spots are faintly visible at 50 mm and very apparent at75mm. Very young redfish are found in protected water with little wave action. There is a distinct avoidance of currents and a preference for isolated grassy clumps or slightly muddy bottom. Young redfish first appeared in primary bays in August (Miles, 1950) but have not been found in the Laguna Madre, a secondary hay, before February. By April, widely scattered aggregations can be found in sheltered grassy areas throughout A Study o/ Redfish and Black Drum Fu;. 2. Larval and juvenile redfish, modified after Pearson, 1929. the Laguna Madre. In early April 1954, many redfish, 1~150 mm long, were <;ap~ tured in boat basins in the Laguna Madre. Subsequent seining revealed that l.arge schools were present in every boat basin, in quiet areas near spoil banks, and in shallow A Study of Redfish and Black Drum isolated sloughs. This occurred in years when salinity was between 40 and 50 %o but during years of lower salinity the fish were scattered over grassy flats as noted by Pear­son (1929), Gunter (1945, 1950), and Miles (1950). The large schools remained in basins until late May when they began to scatter, and by }une no sizable concentrations could be found. This coincided with the movement of small redfish through passes to the Gulf as described by Simmons and Hoese ( 1959) . Returns of tagged fish indicated that many of these small redfish did move toward passes while others moved into primary and secondary bays. Growth. Redfish grow more rapidly than trout or drum. Pearson's (1929) smoothed length frequencies are marked by modal lengths of 300, 530, and 630 mm at the end of the first three years. Gunter (1945) gives the values 400 mm and 600 mm for the first two years while Miles (1950) indicates modal lengths of 320 and 510 mm for these year classes. This later growth rate is substantiated by returns from tagged fish in which the average growth per month was calculated and then prorated for one year (Table 1). TABLE 1 Growth of redfish between the end of the first year and the end of second year as calculated from tag returns. Total length Total length Growth, al one year al two years second year 325 528 203 325 548 223 325 426 101 325 477 152 325 629 304 325 554 229 325 565 240 325 452 127 325 680 355 Mean 325 540 215 Growth, however, is not constant. Length frequencies of 2,000 redfish of year class O from the upper Laguna Madre (Fig. 3) show sporadic growth with a lag in spring, rapid growth in summer. and a slight lag at the end of summer. The large size range during this first year may be due to the long spawning season but there is also sorne variation in the growth of individual fish as evidenced by tag returns. Fig. 4 shows graphically the size of fish when they were tagged, the time freed, and the size at the time of recapture. Table 2, showing the growth of redfish over two years old, indicates a length of 640-730 mm at the end of the third year with a mode of about 730 mm. This result suggest that Pearson's ( 1929) year class IV was year class III and that maturity is reached at the end of the third year. Little is known of growth after three years of age. Miles ( 1951) examined otoliths of a small number of redfish 825-1,000 mm long and noted that those 875 mm long showed six rings while those 925 mm long showed seven rings. Pearson (1929) found small modes at 750 mm and 840 mm and felt that these probably represented year classes IV and V. One tagged redfish, recovered at a probable age of three and one-half years, was 810 mm long. One interesting aspect of growth occurred at Eighth Pass, Mexico where Miles (un­ A Study o/ Redfish and Black Drum "' et: ... .... ... ::1 ..J ..J - ::1 400 350 300 250 200 150 100 50 T 0 TAL LEN G T H F1c. 4. Actual growth of tagged redfish by year classes. TABLE 2 Growth of redfish between end of second year and end of third year. Total length Total length Growth, aL lwo years al three years third year 530 705 175 530 678 148 530 715 185 530 730 200 585 675 90 585 845 260 585 845 260 585 765 180 585 755 170 585 885 300 Mean 563 760 197 A Study o/ Redfish and Block Drum published data) found that redfish of year class O were only 200 mm long in late July. This was 50--00 mm less than comparable fish in the Upper Laguna Madre. Food. Very young redfish subsist primarily on copepods, amphipods and palaemone· tid shrimp. At a size of 100--175 mm the chief food items are small penaeid shrimp, palaemonetid shrimp, small mullet and silversides, small gobies and small crabs. Pearson (1929) covered the area from Matagorda Bay to Baffin Bay and reported shrimp as the chief item in the diet of redfish. Gunter (1945) found that "the blue crab exceeded any other species in number of times found in the stomach and in volume it was far greater than any other food. lt is the principal food of the redfish." He also found grass and wads of amphipods. Knapp (1948) who was primarily concerned with the incidence of menhaden in the diet examined stomachs of fish brought in by charter boat operators at Port Aransas and compiled the data of Wilson, Robinson and Bowers (unpublished reports of the Texas Game and Fish Commission). These data show that over 68 per cent of those redfish with food in the stomach had eaten crabs. Miles (1948-49) ex· amined stomachs of redfish caught in nets thus avoiding contamination of data by bait shrimp from sportsfish catch. He found that crabs, shrimp and small fish were major components of the redfish diet (Table 3). In the Laguna Madre the primary source of food is small crabs. The mud crab, Neopanope texana, and the immature blue crab, Callinecles sapidus Rathbun constitute most of the small crab population of the area and both are utilized to a great extent. Small shrimp, Penaeus azlecus lves, prawns, Palae­moneles inlermedius (Holthuis) and sheepshead minnows, Cyprinodon variegatus Lacépede are utilized to a lesser degree. Oddly enough, redfish do not take crabs used as bait unless the crab is halved and its legs removed. Feeding Habits. Feeding usually takes place in the early morning and late evening often in shallow waters influenced by tides. In sorne cases the water is so shallow that the backs of the fish are visible. Movemenls and Migrations. Pearson (1929), Gunter (1945a), and Miles U950) have described a general migration of redfish to the Gulf during fall months and a fairly rapid return to the bays in spring. These movements do occur but may be less pronounced and cover shorter periods than had been assumed. Records of redfish land­ings by sportsfishermen, by commercial means and by biological nets (Fig. 5) indi­cate that more redfish are present in the bays in spring and fall than in either summer or winter but many are present at all seasons. There was no pronounced migration of redfish through Cedar Bayou Pass in 1950--51 according to the records of a two-way fish trap attended by one of the authors and de­scribed by Simmons and Hoese (1959). Small redfish moved in and out of this pass in June and there was a slightly accelerated outward movement in September and Oe­tober and during suelden drops in temperature. No mature redfish were ever observed moving through the pass although sorne were seen near the Gulf entrance in April and September. Since hay populations do fluctuate it is possible that larger, deeper passes were used. Movement of tagged fish (Fig. 1) show that this movement is random within a hay and that there is little intra-bay movement or bay-gulf travel except perhaps for short periods. Similarly these tagging results show that redfish tagged in the Gulf remained in the Gulf for at least two years and probably permanently. lt is possible that any tagged fish will leave an area and then return but Table 4 shows that the per cent Á Study of Redfish and Black Drum TABLE 3 Food of 1197 redfish, Sciaenops ocellatus, taken at or near Rockport, Texas, from September, 1948, to June, 1949 (after Miles, 1949, 1950) Food item Number Per cent of incidence Unidentified shrimp '1'207 40.0 Shrimp, Palaemonetes spp 136 6.1 Shrimp, Crangon spp 54 1.8 Shrimp, Penaeus spp 11 0.3 Shrimp, Penaeus aztecus '29 0.9 Shrimp, Penaeus duorarum 5 0.16 Unidentified crabs 455 15.0 Blue crab, Callinectes sapidus 50 1.6 Gulf crab, Callinectes danae 21 0.6 Crab, Callinectes spp 20 0.6 'Stone crab, Menippe mercenaria 9 0.3 Spider crab, Libinia dubia 1 0.03 Mud crab, Eupagurus spp 1 0.03 Unidentified fish 4% 16.0 Silversides, M enidia beryllina peninsula 148 4.9 Mojarra, Eucionstomus gula 138 4.6 Flatfish, Paralichthys spp 18 0.6 Anchovy, Anchoiella epsetus 14 0.4 Unidentified eels '14 0.4 Pigfish, Orthopristis chrysopterus '13 0.4 Menhaden, Brevoortia spp 7 0.'23 Mollies, Molliensia spp 5 0.16 Pinfish, Lagodon rhomboides 3 0.10 Pipefish, Syngnathus spp 3 0.10 Catfish, Galeichthys felis 3 0.10 Killifish, Fundulus similis 2 0.06 Croaker, Micropogon undulatus 1 0.03 Blenny, Family Blennidae 1 0.03 Lizard fish, Synodus /oetens 1 0.03 Sea Horse, Hippocampus spp l 0.03 Oyster shell, Ostrea virginica 12 0.4 Squid, Loligo spp 5 0.17 Annelid, N erina agilis 12 0.4 Unidentified vegetation 9 0.29 Isopod, Lavonica spp 7 0.23 Uuidentified snail 2 0.06 Unidentified annelid 2 0.06 Alga e 2 0.06 Gastropod 1 0.03 Turtle grass, T hallassia testidinium 1 0.03 Cricket 1 0.03 recaptured outside the area of tagging is small. It would appear that each hay, when considered on an annual basis, is a closed system. Sorne general movements have been noted during the period from 1952 to the present. Redfish normally move before a strong wind, i.e., move in the direction the wind is blowing, but, when startled, move in to the wind or current. There is. either little move· ment during the day or little feeding as evidenced by the fact that few are caught in nets or on trotlines during daylight hours. Large schools are found in the Gulf. Distribution in Relation to Salinity and Temperature. Redfish are euryhaline and have heen found in fresh water (Gunter, 1942, 1956) and in salinities as high as 159"00 (Simmons, 1957). However, in the Upper Laguna Madre populations were rarely found at salinity. of 50 %o or above and were most abundant at salinities ·OÍ 30-35 %o· One of the investigators (E.G.S.) has transferred small redfish directly from salt water A Study of Redfish and Black Drum 30 1­ z UJ 20 u cr ~ 10 REDFISH CAUGHT PER MAN HOUR WITH ~ 0.2 ROO 8 REEL m :IE i 0.1 JFMAMJJASONO F1c. 5. Catch of redfish by various means, showing relative seasonal abundances. TABLE 4 Recoveries of tagged redfish by year, class, and by area captured Per cent recovered Are a Year Class Within hay where tagged Outside hay Cedar Bayou o I 63.6 9:1 36:4 90.9 27.3% in Gulf 9.1% in Bay All in Gulf Aransas Bay Upper Laguna Madre All o I II 57.1 90.2 95.0 100.0 32.9 16.4% in Gulf 16.Sio/o in other bays 9.8 2.0% inGulf 7.8'% in other bays 5.0 All in Gulf o.o Lower Laguna Madre All 86.0 14.0 .Ali in Gulf into fresh water ponds and eight individuals 600 mm long were captured two years later. Transplants, apparently successful, have been made into the Pecos River and into Lake Kemp but it is not known if these fish will spawn under such conditions. Redfish have heen observed by the authors in waters ranging from 2-33ºC but normally they move into deeper water when extreme temperatures occur. Mass mortal­ity . s~metimes occurs if there is a sud den change in tempera tu re. Su ch "freezes" have heen documented by Gunter (1941) and Gunter and Hildebrand (1951). BlackDrum DESCRIPTION A full des~ription of the black drum, Pogon¡as cromis . (Linnaeus), was given in Jordan and Evennan (1900). Coloration was reported as "gray~sh silvery, with 4 or 5 hroad dark vertical hars, these disappearing with age, usually with no ohlique dark streaks along rows of scaleifabove; fins blackish." In this study the authors found that the coloration of bla:ck drum varies with the age of the fish as well as with its habitat. Th~ typical adult was dark gray with a 'White belly. The characteristic four or five dark vertical bars of younger fish often disappeared with A Study o/ Redfish aná Black Drum age as noted above. Drum residing in the Gulf took on an almost uniform silvery ap­pearance and lost the vertical bars at an early age while those residing in bays tended to become darker than their Gulf counterparts and are often bronze along the back and dirty white on the sides and belly. Breuer captured many drum in the turbid water of Baffin Bay. These were normally nearly jet black on the sides.and back and hada gray belly. lt was noted in Baffin Bay that many of the jet black drum were malformed, either by loss of eyes, mechanical damage to mouth or with deformed backbones. In contrast malformed drum in the Upper Laguna Madre did not exhibit the jet black appearance but possessed normal coloration. lt is possible that many of the malformed drum in the Upper Laguna Madre received injuries from hoat props. The senior author has observed commercial fishermen run motorboats through schools of drum feeding in shallow water, then go hack and pickup a tubful of injured fish. Dr. William McFarland reports (verbal communication) that severance of certain nerves in the head of sorne sciaenids brought about an enlargement of the chromato­phores in the general area of the nerve severance. The high incidence of malformed jet hlack drum in Baffin Bay could be due to the inability of injured fish to follow usual migrations, and are thus restricted to this turbid a rea. DISTRIBUTION Black drum occur along the Atlantic coast and Gulf coast from New York to the Rio Grande River and have been reported straying as far north as Massachusetts. Hildebrand (personal communication) reported finding none at Vera Cruz. Black drum are found in the bays even more than redfish; nevertheless a sizable population exists in the Gulf of Mexico. By far the heaviest concentrations are usually found in Corpus Christi Bay and in the Laguna Madre. Joseph and Yerger (1952) noted black drum rare at Alli· gator Habor, Florida, especiq.lly in summer. Frisbie (1961) indicated that young drum were relatively uncommon in the Chesapeake and Delaware Bay regions and that these young were normally found in fresh to brackish waters. LIFE HISTORY Black drum reach sexual maturity at the end of the second year when approximately 320 mm long. Spawning occurs in or near passes, in the Gulf, and in all hay areas. Miles (1950, 1951) reported that mature drum remained in bays until nearly ripe before migrating toward passes and, after spawning, quickly returned to their preferred hay habitat. Sciaenid eggs, believed to be those of black drum, were found on March 20, 1952 near the Point of Rocks, and on the same date ripe drum were found in Baffin Bay. Other eggs were found throughout the upper Laguna Madre. Sorne of the ripe drum tagged near Baffin Bay remained in that locat~on throughout the spawning season. Others moved into Corpus Christi Bay. In April 1960, eggs were stripped from a 40 pound drum and used for comparison with eggs taken in plankton tows. Developing eggs (Fig. 6) were found to be present in hay areas from February through April. Ripe fish have heen found as early as December (all males) andas late as }une, but 90 per cent of the known spawning occurs in February and March. However, length frequencies "· ' '~ A Study o/ Redfish and Black Drum o o • ºº o F1c. 6. a. Unfertilized eggs taken from ripe drum, April 12, '1960. b,c,d. Eggs taken in plankton tows, February-April, 1960. (Fig. 7) indicate that there may be a split or very late spawning in June or July. This was also suggested by Pearson ( 1929) . Descriptions and H abits o/ Y oung, Early Development. Pearson ( 1929) gives the following description of young drum. "The larval drum begins to take on the general appearance of a drum when it reaches a length of about eight millimeters. Black chromatophores appear EACH DATA POINT FOR A 10 mm tNTERVAL r ........ ~ , ..... ______ ---­ "º •OO •50 F1c. 7. Length frequencies of black drum caught in nets in the upper Laguna Madre. A Study of Redfish and Black Drum in great abundance along the back and sides of the fish and tend to arrange themselves into definite groups. These groups then arrange themselves into the six vertical bars which will serve to identify the immature black drum. The general adult shape is attained when the fish reaches 15 millimeters-.The black bars are well defined, the fins generally colorless, and the barbels on the lower jaw in evidence. Ata length of 25 millimeters, the pectorals and anal fins take on a dark cast, the entire fish gradually becoming darker." Pearson first located the larval drum of 9 to 37 mm (Fig. 8) along the shores of Corpus Christi Bay near the channel entrance to Oso Bay on May 13, 1926. He noted, however, that still smaller fish were found near passes to the Gulf. Many schools of small drum, approximately 50 mm long, were noted in the Laguna Madre at the en­trance to Baffin Bay in June and July 1951, and even smaller drum, only 13-18 mm long, were found in the Upper Laguna Madre in May and June. These smaller drum were invariably located in channels, stagnant sloughs or boat basins. Many young drum, 130-180 mm long, were located in the Upper Laguna Madre in May and the same size fish were found in Baffin Bay and the Lower Laguna Madre from September through December. It appears that spawning and nursery grounds can be the same. Drum tend to enter a preferred habitat and to remain there. This type habitat, represented by all of the Laguna Madre and Baffin Bay and much of the shallow water of Corpus Christi, Nueces and Oso Bay, is utilized by the O year class as well as ali other year classes including the largest sizes. Growth. Considerable confusion exists concerning the growth rates of black drum. Pearson (1929) considered that fish just entering the second year had reached a fork length of 250 mm but stated that catches of fish 150 mm long in December were difficult to interpret and might be due to a late spawning or possibly a split spawning. This same situation was found to exist during later surveys. Drum only 13-18 mm long were found in late May and J une when fish from the winter spawning were 50-75 mm .. long. At the same time definite modes (Fig. 7) were found at 175 mm and 240 mm. In February and March these same modes were found, though less pronounced. If 175 mm fish were the result of a split spawning in summer, they would represent one year old fish; if they were the result of a late spawning they would be slightly over one year old. It seems probable that late or split spawning does occur, and that a standard length of 140­180 mm is reached in one year 210-250 mm in one and one-half years, and 290­330 mm. in two years . .Although peaks are masked by overlapping there is evidence (Fig. 7) that drum reach a length of 400-430 mm in three years. Beyond that, tag returns, (Fig. 9) indicate a growth of about 50 mm per year. Food and Feeding. The food of very young drum consists chiefly of marine annelids, small fishes and soft crustaceans. Larger drum feed on molluscs and shrimp. Pearson (1929) reported that the adult black drum's food was primarily mollusks and crabs while Miles (1949) showed that drum in Aransas Bay feed heavily on shrimp, mollusks, vegetation and crabs and only slightly on fish. (Table 5). In the Upper Laguna Madre and Baffin Bay ali drum examined (about 1,000) had been feeding on small mollusks, and much dead shell had been consumed. Near Baffin Bay drum were found to be feeding on dead shell to which Acetabularia crenulata Lamarck and other algae were attached. Another food itero was the sheepshead minnow, Cyprirwdon variegatus Lacépede, which was taken in very .shallow water. In a few instan.ces polychaetes were found packed A Study of Redfish and Black Drum F1G. 8. Juvenile and adult black drum modified after Pearson (1929). in the stomachs of fish examined and this coincided with lunar swarming of these small worms. In the lower Laguna Madre, salinity is less extreme and more spec~es of mol­lusks are present. Species consumed include Brachiodontes exustus Linnaeus, small Aquipecten irradians amplú:ostata Dall, Laevú:ardium morwni Conrad, Anomowcardia cuneimeris Conrad, and Mulinia lateralis Say (Fig. 10). While drum were observed feeding on or near oyster reefs, sto'machs taken from these dram contained no oysters but rather a small mollusk, Brachiodontes exustus. Most of the drum's food is taken from the bottom or from below the bottom. Mollusks A Study of Redfish and B/,ack Dnun ºo, • • • ", , • 1 o" o 1 '" • "' 1 • 1 o• o • •" • 111 1 1 • 1 o • o 1 • • • F1c. 9. Growth of tagged black drum. TABLE 5 Food of 189 Drum, Pogonias cromis, taken at ornear Rockport, Texas from September, 1948 to June, '1949 (after Miles, 1949, 1950) Food ítem Number Shrimp, Penaeus aztecus 3 Shrimp, peneid type 2 Crab, Callinectes sp. 2 Crab, Callinectes sapidus 3 Pin Perch, L. rhomboides 1 Cyprinodon sp. 1 Venus clam, Venus mercenaria 5 Razor clam, Tagelus gibbus í Oysters shell 3 Venus sp. 5 Muliniasp. 4 Bullasp. 2 Donax variabilis 1 Annelids 1 Grasses 1 Algae, unidentified 1 Unidentifiable mass• (no. of stomachs) 49 • SS shrimps, 12 crabs, 9 6sh, and 20 mollusks cooslituted the unidenti6able organisms. are grubbed from mud or sand and crushed with strong phary"ngeal teeth (Fig. 11). Crabs were treated in the same manner but sheepshead minnows were swallowed intact. Since mollusks are one of the favored foods of drum and since this food is often found under beds of vegetation, the normal feeding habits of drum are considered detri­mental to these "grass" beds and consequently to sea trout, small redfish, and juvenile shrimp which use these areas as spawning or nursery grounds. Movements and Migrati.ons. Black drum are commonly found in hypersaline waters but can adapt quickly to wide ranges in salinity. A tendency for drum to move into streams inlets has been described by Breuer (1957) . With the possible exception of spawning migrations this temporary surge to fresh water is the most pronounced and positive of ali drum movements. There is also a constant movement in search of food and the fish often travel in large schools during these periods. When food is abundant there is little intra-bay movement. Of the 94 recovered tagged fish from the Laguna Madre and Baffin Bay (Fig. 12), 56 fish or nearly 60 per cent, were recaptured within five miles of the site of tagging. lt must be noted that sorne of these fish were free for over A Study of Redfish and Black Drum F1c. 10. Items commonly used as food by black drum. Left to right, top row: Chione cancel/ata, Lithophaga paprecea, Aquipecten irradians amplicostatus, Brachiodontes exustus; Bottom row: Laevicardium mortoni, Anomalocardia cuneimeris, Mulinia lateralis. two years and may have migrated greater distances. Eight fish moved southward into the Lower Laguna Madre and eight more were recaptured in Corpus Christi Bay. The movements northward are attributable to spawning but the cause for the southward movement is not known. Movement may be accelerated by adverse conditions. In 1952 most tagged fish were recovered in the Laguna Madre. Ín 1953 hypersalinity and high temperatures destroyed most bivalves in the Upper Laguna Madre and a mass exodus of drum occurred. Tag returns indicate that these fish moved as far north as San Antonio Bay and returned to the Laguna Madre when food again became available. The longest migration recorded to date was from the central Laguna Madre to Texas City near Galveston, a distance of 245 miles covered in one year or less. Breuer has noted that in the Lower Laguna Madre small drum are present ali year and these move northward as spring approaches. At the same time large drum enter the hay at Brazos Santiago Pass and move northward. Shortly after this large schools appear in the lower section of the Upper Laguna Madre although too few fish have been tagged in the lower lagoon to verify· the origin of these schools. There has been move­ment of at least 10 tagged fish southward from the Upper Laguna Madre into the Lower Laguna Madre during fall and winter months. These seasonal movements are complicated by the fact that there was a northward movement of tagged drum out of the Upper Laguna Madre during spring months (Fig. 12). Very large drum are present in the entire Laguna Madre all year but are less abundant during summer months, at least in the Upper Laguna Madre. This is illustrated by cree! census data (Simmons, 1959--óO) which recorded an average weight of 15.0 pounds for drum caught in February and March compared to 2.0 for those caught in June or July, 1959. Distribution in Relation to Salinity and T emperature. Black drum are euryhaline and frequently inhabit brackish or even fresh water (Gunter, 1956). Adults were found in August, 1953 at salinities as high as 80 %o although many fish had glazed eyes and sorne even were blinded and had lesions on the body. Wide ranges in temperature are also tolerated, and schools have been found by the senior author apparently' thriving, in turbid water only four inches deep where the temperature was 35ºC. A sudden drop in water temperature causes movement to deeper water as in 1958 when drum from the upper Laguna Madre moved into Baffin Bay and Corpus Christi Bay. Water temperature at that time was 3ºC and sorne of the fish were stunned but still capable of swimming. However, mass mortality is not uncommon when water temperature drops quickly and conditions remain adverse for long periods. Un­ published data of the Texas Game and Fish Commission indicates that during a five day "freeze" in 1951 more drum were killed than trout and redfish combined. The rapidity of recovery of drum populations is evidenced by the fact that gill net sets in October, 1951 caught only four drum while similar sets in the summer and fall seasons of 1952 caught between 138 and 426 drum per month (Simmons, 1952). lt is further shown by U.S. Fish and Wildlife Service reports which lista decline in drum landings for the State of Texas from 708,300 pounds in 1950 to 702,200 pounds in 1951, while redfish landings dropped from 567,200 pounds to 237,000 pounds. Drum landings dropped only one per cent while redfish landings dropped 58 per cent. Parasites Ectoparasites are fairly common on both redfish and drum of all sizes. They are normally' absent when the fish is in hypersaline water above 45 %o (Simmons, 1957). Among these parasites are the copepods Caligus repax Milne Edwards, C. bonito Wilson, C. latifrons Wilson and Bra.chiella gulosa Wilson, all from the upper Laguna Madre. Causey (1955) also lists Caligus pelamydis Kroyer and BrachieUa macrura Wilson from drum and Echetus typicus Kroyer and Lernanthropus paenulatus Wilson from redfish in the vicinity of Port Aransas. The only isopod found on sciaenids during this study in the Laguna Madre was N erocila acuminata Schioedte and Neinert. The most important interna! parasite found in these fishes is the "Spaghetti worm" which appears to be similar to Poecilancistrium rob·ustum Chandler, a pleurocercoid described from the muscle mass of Cynoscion nebulosus in Galveston Bay by Chandler (1935). These worms from trout are discussed by Parker (1951) and by Guest and Gunter (1958) They occur in the muscle mass of both redfish and drum and are more noticeable in large drum. The appearance of this worm in drum is the cause of objection by the public to its use as a food fish. However, the smaller fish are relatively free from this parasite--which is not harmful to humans in any state. (Parker, 1951) So­gandares-Bernal and Hutton (1959) reported helminth parasites from other members of this family and it is probable that sorne of these also occur in drum and redfish. SPORT FISHERY Sports fishing in Texas waters has increased tremendously in recent years with the advent of larger boats and motors. Bait stands have reported a three-fold increase in the number of boats rented and launched. A survey made by Belden Associates (1959) indicates sport fishermen caught 9,199,000 pounds of redfish and 4,343,000 pou~ds of drum from September 1, 1957 to August 31, 1958. Cree! census data from the upper Laguna Madre indicates a much smaller catch. During the period from August 1, 1959 to July 31, 1960 a total of 82,992 fishermen caught 39,536 redfish weighing 78,058 pounds in this hay which has a water area of about 100 square miles. At the same time 18,298 drum weighing 37,030 pounds were caught. If these values are expanded to cover the entire year and the entire State the catch would be about 975,000 pounds of redfish and 540,000 pounds of drum. Virtually ali of the redfish captured were less than three years old and many' were less than one year. Drum were caught in ali sizes and ages. This species is not actively sought and less than 10 per cent of Laguna Madre fishermen fished exclusively for drum although many incidental catches were noted. Tagging results (Table 6) indicate a heavy fishing pressure for redfish and, per· centagewise, a larger portion of the population harvested than for any other species. These redfish tag returns were primarily contributed by sports fishermen, hut ¡;orne were from trot line operators. In spite of the heavy fishing pressure, and even if the assumption is made that only 50 per cent of the recovered tags were turned in, fishing mortality for redfish is not over 30 per cent. Isolated schools of redfish, however, may have much greater mortality'. In one instance April 24, 1951, 134 redfish from a single school were cap tu red, tagged, and released. 22.3 % were recove red, 80% within one year. If it is again assumed that 50 per cent of the recovered tags were turned in, the A Study of Redfish and Black Drum TABLE 6 Comparison of tag recoveries for redfish and drum Area 1) Redfisb tagged Reco"·ered Per cenl recovered Drum lagged Reco,·ered Per cenl recovered Cedar Bayou Aransas Bay Upper Laguna Madre (Year Class O only) 322 152 932 43 17 43 13.3 11.1 4.6 93 31 4 0= 4.3 o Upper Laguna Madre (Ali other Y ear Classes) Baffin Bay Lower Laguna Madre 502 155 60 6 11.1 6.0 8,205· 780 68 25 0.8 3.2 fishing mortality would be about 50-60 per cent. 26 were recovered from sports fisher­men; 4 were recovered from commercial fishermen. Springer and Pirson (1958) stated that at Port Aransas, Texas, redfish are caught throughout the year but the peak months occurred in the fall when an outward migra­tion occurred. Large catches were also reported in July and August. This is somewhat similar to the situation in the Laguna Madre where the fall and spring months are most productive. It is difficult to determine the actual number of redfish caught in the surf since so much of the beach is now accessible, but reported landings at Port Aransas of 6,964; 4,567; 9,644; 3,369 and 1,840 fish during the years of 1952, 1953, 1954, 1955 and 1956 are probably indicative of the catch along this beach. Black drum were caught at Port Aransas throughout the year, but the best catches occurred from October to February with the highest peak in November. Catches of 1,974; 4,321; 4,055; 1,741 and 1,181 fish were noted for 1952, 1953, 1954, 1955 and 1956. Although both redfish and drum are primarily bottom feeders, fishing techniques differ for the two species. Redfish are caught in potholes on the grassy flats, near oyster reefs, near passes, and occasionally in boat basins. In the Upper Laguna Madre and in sorne of the channels of the lower Laguna Madre small redfish are caught in the spring. However, the larger fish must be sought in the almost inaccessible shallow flats, particularly in the lower lagoon where fishermen use shallow draft boats to reach the fish. In Baffin Bay redfish contribute a great 'ºo ~ o ¡I 1 -: :;; 1\ \ / X •O 0 X I \ .\' 1 I . . . / . ·­ 300 . : o- o . : I o I . . . 200 -= - ~ - - - X / : =; = . = 1 00 .­ O R x- ~ ~ . '!.­ - "'\ .o -­ ~ N ~ o o . ~ . N N • n Y E AR a> ., Frc. 13. Commercial landings, X redfish and black drum, for the State of Texas ; 197 2 factors which influenced landings are indicated. A Study of Redfish and füack Drum Hypersalinity in the Laguna Madre in the summer of 1937 killed many of the fish in that hay and the catch of redfish, and more notably drum, dropped accordingly during the next two years. Before populations had time to recover, the Texas coast was struck, in 1940, with one of the most severe blizzards in history. Gunter ( 1941) stated that water temperature fe]] to 39ºF and there was considerable ice along the shore. Fish were packed in windrows ali along the shores of the bays and millions of pounds were destroyed. Commercial landings fell to the lowest level in history. A minor kili dueto freeze occurred in 1941, a heavy one in 1947 and other minor ones in 1948 and 1949. Ali of these tended to keep the leve] of landings below those of prior years. In late Janu­ary, 1951 another severe blizzard struck the coast with air temperature from January 29 to February 3, of 25, 22, 22, 18, 20, and 19ºF for consecutive days (Gunter and Hilde­brand 1951). Dead fish were checked by Game and Fish Commission biologists immedi­ately after this freeze and it was estimated that from 60 to 90 million pounds of fish were killed. This dropped redfish landings to a further low ebb but lowered drum landings very little. Another factor influencing commercial fishing is legislative opening and closing of bays to net fi shing. Most Texas bays, with the exception of the Laguna Madre, were closed in 1925 but severa! were re-opened at later dates. The Laguna Madre was closed by sections starting in 1931 with Cameron County' being the last to close. In 1959 severa] large bays remained open but much of the perimeters of these bays and practi­cally ali of the shallow bays, where fishing with nets is most successful, were closed. 1 t must be noted that, as use of nets decreased use of trotlines increased. Breuer (un­published data) conducted a survey a survey of trot line fishermen in the lower Laguna Madre and found that in September 1959, eight trot liners fished 24,500 hooks and caught 14,113 pounds of redfish and 5,131 pounds of black drum. In that area the main­line is suspended above the water between poles and the drops or stagings extend clown with the hooks just under the water. The bait, usually a colored piece of plastic, is moved by waves and is effective in taking both redfish and drum. In the lower Laguna Madre this method is geared primarily for the taking of redfish with drum being caught inci­dentally. Supplemental lines, baited with live perch or cut fish, are effective in taking larger redfish and large trout. In the upper Laguna Madre, fishing is geared to the taking of drum with redfish incidental. Bottom lines, baited with shrimp, are often used as a supplement to high lines. Mr. John R. Beasley, of Beeville, Texas has compiled the catch of redfish and drum by various means in 1956. These data presented show that nearly 34 per cent of the redfish and over 46 per cent of the drum landed commercially were taken on trot lines. Commercial production of fish in Texas has changed in location completely since the turn of the century. At one time the Laguna Madre supplied less than two per cent of the commercial landings for Texas; since that time the Laguna has become the leading pro­ducer for the state. Table 8, compiled by Mr. Beasley, shows the catch for the Laguna Madre as compared to that of ali the other bays in Texas. The only time more drum were landed from any single hay than from the Laguna Madre was in 1956-57 and 1957-58 when heavy rainfall flushed out the lagoon and the fish spread into the Gulf and into the Aransas-Corpus Christi Bay area. While the normal trot line procedure of commercial fishing may contribute signifi­cantly to a suitable harvest of redfish and while the percentage of black drum taken hy A Study o/ Redfish and Black Drum TABLE 8 Pounds of Redfish and Black Drum caught in the Laguna 'Madre as compared to the rest of the Texas coast for a period of 2"2 years. Compiled by 1. R. Beasley, Beeville, Texas. Year Regio o Red6sh Drum Totals Year Regio o Red6sh Drum Totals 1936-37 Laguna 373,357 1,227,200 1,600,557 Bal. coast 288,217 348,705 637,022 1937-38 Laguna 345,581 1,330,901 1,676,452 Bal. coast 416,076 í7i,991 1,194,067 1938-39 Laguna 2'29,772 993,649 l,123,421 Bal. coast 181,074 464,418 640,465 1939--40 Laguna 142,998 507,187 650,185 Bal. coast 141,181 117,597 258,778 1940-41 Laguna 94,453 421,158 515,611 Bal. coast 119,661 58,268 17i,929 1941-42 Laguna 517,806 627,844 1,145,650 Bal. coast 223,09'2 110,409 333,501 1942-43 Laguna 598,700 963,779 1,562,487 Bal. coast 368,339 133,198 501,537 1943-44 Laguna 382,033 i86,578 1,169,611 Bal. coast 448,116 153,42'"2 601,538 1944-45 Laguna 432,120 783,299 1,215,419 Bal. coast 511,434 216,448 727,882 1945-46 Laguna 314,553 689,617 1,004,170 Bal. coast 417,549 500,633 926,193 1946-47 Laguna 304,713 454,578 759,291 Bal. coast 185,696 203,836 389,532 1947-48 Laguna 212,839 219,009 431,848 Bal. coast 249.413 221,744 471,187 1948-49 Laguna 309,227 363,735 672,962 Bal. coast 158,761 168,653 327,414 1949-50 Laguna 170,401 2'.2"2,521 392,92"2 Bal. coast 304,067 3"22,047 626,114 1950-51 Laguna 101,532 429,436 530,968 Bal. coast 199,882 161,301 361,183 1951-52 Laguna 79,663 290,319 369,982 Bal. coast 199,882 161,301 361,183 1952-53 Laguna 131,869 406,92'2 538,791 Bal. coast 227,256 261,948 489,204 1953-54 Laguna 223,039 262,701 485,740 Bal. coast 176,065 132,855 308,204 1954-55 Laguna 328,520 838,195 1,166,715 Bal. coast 125,553 146,563 272,126 1955-56 Laguna 292,962 609,358 90'2,320 Bal. coast 124,505 140,655 265,160 1956-57 Laguna 208,153 465,939 674,092 Bal. coast 158,092 83"2,439 990,531 1957-58 Laguna 237,280 134,094 371,374 Bal. coast 195,633 500,091 695,724 TOTALS Laguna Bal. coast 6,031,579 5,333,295 13,028,019 6,189,053 19,239,598 11,523,148 TOTAL SEA TROUT, REDFISH ANO BLACK DRU!\l: 49,310,841 ESTIMATED LOSS IN 1951 FREEZE: 60,000,000-90,000,000 this method may amount to a significant portion of the total commercial hay catch, this fishing procedure cannot begin to approach a suitable harvest of the total available black drum population. The black drum population of the Laguna Madre is extensive and since the normal feeding habits of drum are considered to be detrimental to important vegetation of the area, a program designed to effect a suitable drum han-est has been initiated in the lower Laguna Madre. In 1957, the hay waters of Cameron County were opened to contract A Study of Redfish and Black Drum commercial fishing for drum during the months of December, January and February of each year using accepted gill nets. In 1959, Willacy County joined with Cameron County but for the months of January through May of each year. Under this program, contracts are let by the Game and Fish Commission to persons for the express purpose of taking black drum from the hay waters of these counties. Hours of operation, gear to be used, keeping of records and license requirements are governed by strict rules and regula· tions. These are agreed to by the contract applicants before the contract is let, to mini· mize any adverse effects on other species of marine life and to vegetation and hay bot· toms. The program was recommended to improve and to decrease the detrimental effects caused by an overabundant drum population. Summary l. Data on two of the most important food and game fishes of the Texas coast, the redfish and the black drum, are summarized. 2. Redfish range from New Jersey on the Atlantic to Tuxpan, Mexico in the Gulf of Mexico. Drum are found from New York to as far south as South America. 3. Spawning of redfish occurs in the Gulf of Mexico, possibly near passes, in fall months. Young fish move through passes into the bays which serve as nursery grounds. 4. Growth is rapid; standard lengths of 320, 530, and about 700 mm being reached in the first, second and third years. S. Food consists primarily of various crabs, fishes and shrimp. As size of the redfish increases the percentage of crabs eaten also increases. 6. There is little movement of these fishes between bays and even less between hay and gulf. Apparently sorne redfish move to the gulf when less than one year old and never re·enter bays. There are minor movements each day between feeding grounds and deeper water. 7. Redfish are euryhaline but are most often found at 20--45 %o· Considerable fluctu· ation in temperature is tolerated if changes are gradual but many fish are destroyed by sudden cold spells. 8. Spawning of the black drum occurs in and near passes and in many shallow hay areas. While 90 per cent of the spawning occurs in February and March, sorne spawning has been noted as early as December with a secondary spawning in May and June. Milt and eggs are dropped in any location while schools of fish are moving. Spawning and nursery grounds can be the same location. 9. Standard lengths of 160, 310 and 415 mm in one, two, and three years respectively, are attained. Beyond the third year, growth continues at the rate of 50 mm per year. 10. Food of the black drum consists principally of small mollusks, crabs and vegeta· tion with lesser amounts of shrimp, polychaete worms, and small fish being consumed. 11. There is little movement of drum from hay to hay or from hay to gulf. 12. While the black drum is capable of tolerating almost any salinity range encoun· tered from 10 to 85 %0, ·the usual range is 25 to 50 %0• Temperature fluctuations can be tolerated if they are not too rapid, too severe or too prolonged. 13. Both redfish and drum are parasitised extensively by the "spaghetti worm" and to a lesser degree by copepods and isopods. 14. Redfish are sought by most sport fishermen and cree! census data indicates a A Study of Redfish and Black Drum harvest of about one million pounds per year for hay areas. Drum are sought less ex­tensively. 14. Due to the bottom feeding habits of both fish, most are captured on dead bait or sub-surface artificial lures. Tag returns show that a much larger per cent of the total population of redfish is harvested than of drum. 15. Both redfish and drum are taken commercially by nets, trot lines and rod and reel. Since legislative closure of bays to net fishing, the use of trot lines has been intensi­fied. From a position of little commercial importance, the Laguna Madre has become the leading area in commercial landings. Fluctuations have been caused by such factors as mass mortality from freezes, hypersalinity and by the opening and closing of bays to nets. 16. Total commercial landings for trout, redfish and drum for the last 22 years in Texas were just under 50 million pounds while the mortality from the freeze of 1951 alone was 60 to 90 million pounds. Since 1936, the average annual commercial landl.ngs on the Texas coast have been 516,585 pounds of redfish and 873,544 pounds of drum. 17. Drum population recovered from freezes more rapidly than redfish and within two years overpopulations existed. Overpopulations tended to be detrimental to redfish, trout and brown shrimp as the normal feeding habits of drum destroy vegetation which serves as spawning and nursery grounds for these species. In an effort to alleviate over· population, rough fish permits for drum only, have been issued for certain parts of the Laguna Madre. Acknowledgments Grateful appreciation is expressed to all members of the Marine Fisheries Division of the Texas Game and Fish Commission who aided in the typing and preparation of this manuscript. Unpublished data from field work by D. W. Miles were made available from Commission files. Dr. Henry Hildebrand of the University of Corpus Christi offered valu­able information concerning distribution of fishes and Mr. John R. Beasley of Beeville, Texas contributed much to the statistics contained in the commercial section. Miss Sandra Pounds prepared the illustrations. Unusual taxa were identified by Thomas E. Bowman, U. S. National Museum. Literature Cited Anderson, A. W., and C. E. Peterson. 1952. Fishery Statistics of the U. 'S. 1949, U. S. Fish and Wildlife Service Statistical Digest No. 25, Anderson, A. W., and C. E. Petetson. 1953. Fishery Statistics of the U. S. 1950, U. S. Fish and Wildlife Service Statistical Digest No. 27. Anderson, A. W., and C. E. Petei:son. 1954. Fishery Statistics of the U. S. 1951, U. S. Fish and Wildlife Service 'Statistical Digest No. 30. Anderson, A. W., and A. E. Power. '1949. Fishery Statistics of the U. S. 1945, U. S. Fish and Wildlife Service Statistical Digest No. 18. Anderson, A. W., and A. E. Power. 195'1. Fishery 'Statistics of the U. S. 194-S, U. S. Fish and Wildlife Service Statistical Digest No. 22. . Anderson, A. W., and A. E. Power. 1955. Fishery Statistics of the U. 'S. 1952, U. S. Fish and Wildlife Service Statistical Digest No. 34. Anderson, A. W., and A. E. Power. 1956a. Fishery Statistics of the U. S. 1953, U. S. Fish and Wildlife Service Statistical Digest No. 36. Anderson, A. W., and A. E. Power. 1956b. Fishery 'Statistics of the U. S. 1954, U. S. Fish and Wildlife Service Statistical Digest No. 39. A Study of Redfish and Bl,ack Drum Anderson, A. W., and A. E. Power. '195.7. Fishery Statistics of The U. S. 1955, U. S. Fish and Wildlife Service Statistical Digest No. 41. Belden Associates. 1959. The Salt Water Fish Harvest of Texas Sportsmen. September 1957-August 1958. Breuer, Joseph P. 19S7. Ecological survey of Baffin and Alazan Bays, Texas. Pub!. lnst. Mar. Sci. Univ. Tex. 4 (2) : 134-155. Causey, David. 19515. Parasitic copepods from Gulf of Mexico fish. Occas. Papers Louisiana State University Mar. Lab., No. 9, p. 'l'-19. Collins, J. W. 1892. 'Statistical review of the coast fisheries of the United States. Report of the U. S. Commissioner of Fisheries from 1888, part 16, appendix 2: 271-378. VI. Fisheries of the Gulf States. Collins, J. W., and Hugh M. Smith. 1891. A statistical report on the fisheries of the Gulf States. Bull. U. S. Fish. Comm. 11: 93-184. Chandler, Asa C. 1935. Parasites of Fishes in Galveston Bay. Proc. U. S. Nat. Museum, Vol. 83, 1935. Fiedler, R. H. 1938. Fishery industries of the U. S. 1937. U. S. Bureau of Fisheries Adm. Rept. No. 32. ----. 1940. Fishery industries of the U. S. 1938. U. S Bureau of Fisheries Adm. Rept. No. 37. ----. 1941. Fisheries industries of the U. 'S. '1939. U. S. Bureau of Fisheries Adm. Rpt. No. 41. ----. 1943. Fisheries statistics of the U. S. 1940. U. S. Fish and Wildlife Service Digest No. 4. Frisbie, C. M. 1961. Y oung black drum, Pogonias cromis, in tidal fresh and brackish waters, especially in the Chesapeake and Delaware Bay areas. Chesapeake Sci. 2: 94-100. Guest, William C., and Gordon Gunter. 1958. The Sea Trout or Weakfishes (Genus Cynoscion) of the Gulf of Mexico. Gulf States Marine Fisheries Commission Technical Summary No. 1. Gunter, Gordon. 1938a. The relative numbers of species of marine fish on the Louisiana coast. Amer. Nat. 62: 77--83. ----. 1938b. Seasonal variations in abundance of certain estuarine and marine fishes in Louisiana, with particular reference to life histories. Eco!. Mongr. 8: 313-346. ----. '1941. Death of fishes due to cold of the Texas coast. Ecology 22(2): 203-208. ----. '1941. Relative number of shallow water fishes of the northern Gulf of Mexico, with sorne records of rare fish from the Texas coast. Amer. Midl. Nat. Zti: 194-200. ----. 1945. Studies on marine fishes of Texas. Pub!. lnst. Mar. Sci. Univ. Tex. 1(1): 1-90. ----. 1950. Correlation between temperature of water and size of marine fishes on the Atlantic and Gulf coasts of the United States. Copeia 1950 ( 4): 298-304. ----. 195'2. The import of catastrophic mortalities for marine fisheries along the Texas coasL J. Wildlife Mgmt. 16(1) : 63-69. ----.1956. A list of the fishes of the mainland of North and Middle America recorded from hoth fresh and sea water. Amer. Midl. Nat. 28: '20!>-226. Gunter, Gordon, and H. H. Hildebrand. 1951. Destruction of fishes and other organisms on the south Texas coast by the cold wave of January 28-February 3, 195'1, Ecology 32(4): 73'1-73S. Gunter, Gordon, R. H. Williams, C. C. Davis and F. G. W. Smith. 1948. Catastrophic mass mortality of marine animals and coincident phytoplankton bloom on the west coast of Florida, November 1946--May 1947, Eco!. Monog. 18 : 309-324. Hildebrand, H. H. 1954. A study of the fauna of the brown shrimp (Penaeus aztecus lves) grounds in the western Gulf of Mexico. Pub. lnst. Mar. 'Sci. Univ. Tex. 3 ('2) : 233-366. ----. 1955. A study of the pink shrimp (Penaeus duorarum Burkenroad) grounds in the Gulf of Campeche. Pub!. lnst. Mar. Sci. Univ. Tex. 4(1'): 169'-232. Jordan, David Starr, and B. E. Evermann. 1898-1900. The fishes of north and middle America. Bull. U. S. Nat. Mus. No. 47, 3313 p. Joseph, Edwin B., and Ralph W. Yerger. 1952. The fishes of Alligator Harbor, Florida, with notes on their natural history, Papers from the Oceanographic lnstitute, Florida State University 'Studies No. 22: '11-156. Knapp, Frank T. 1948. A partía! analysis of the Texas menhaden problem with notes on the food of the more important fishes of the Texas Gulf coast. Texas Game, Fish and Oyster Commission, Marine Laboratory, Annual Report, 1948--49, p. 101-127. (Mimeographed.) Mansueti, R. J. 196'1. Restriction of very young red drum, Sciaenops ocellata. to shallow estuarine waters of Chesapeake Bay during late autumn. Chesapeake Sci. 2: 207-210. A Study o/ Redfish and Black Drum Miles, Dewey W. 19419. A study of the food habits of the fishes of the Aransas Bay area. Texas Game, Fish and Oyster Commission, Marine Laboratory Annual Report, 1948-49, p. 126-169. (Mimeographed.) ----. 1950. The life histories of the Spotted 'Sea Trout, Cynoscion nebulosus, and the Redfish, Sciaenops ocellatus. Texas Game, Fish and Oyster Commission, Marine Laboratory, Annual Report, 1949-50. (Mimeographed.) ----.. 1951. T·he life histories of the Sea Trout, Cynoscion nebulosus, and the Redfish, Sciaenops ocellatus: 'Sexual behavior. Texas Game and Fish Commission, Marine Laboratory Annual Report, 199(}-Sl. (Mimeographed.) Parker, R. H. '1951. Why those wormy trout? Tex. Game Fish, June, 1951 : '2-3. Pearson, John C. 1929. Natural history and conservation of redfish and other commercial sciaenids of the Texas coast. Bull. Bur. Fisheries 44: '129-'214. Simmons, E. G. 195lb. The Cedar Bayou fish trap. Texas Game and Fish Commission, Annual Report, 1950-Sl, l...J26. ----. 1957. An ecological survey of the upper Laguna Madre of Texas. Pub!. lnst. Mar. Sci. Univ. Tex. 4('2): 156-200. ----. 1961. Evaluation of sportsfish catch and recall methods of survey. In Project Reports, Marine Fisheries Division, Texas Game and Fish Commission, 1959-60. Siinmons, E. G., and JI. D. Hoese. 1959. Studies on the hydrography and fish migrations of Cedar Bayou, a natural tidal inlet on the central Texas coast. Pub!. lnst. Mar. Sci. Univ. Tex. 6: 56-80. Soganderes-Bernnl, Franklin, and Robert F. Hutton. 1959. Studies on ·helminth parasites of the coast of Florida. l'. Digenetic trematodes of marine fishes from Tamp'a and Boca Cieca Bays with descriptions of two new species. Bull. Mar. 'Sci. Gulf Carib. 9 ( l) : 53-68. Springer, Víctor G., and Jacques Pirson. 1958. Fluctuations in the relative abundance of sports fishes as indicated by the catch at Port Aransas, Texas 1952-1956. Pub!. lnst. Mar. Sci. Univ. Tex. 5: '169-185. Townsend, C. H. 1899. Statistics of the fisheries of the Gulf states. Report of the U. S. Commissioner of Fisheries, Part ·z5: 105-169. Sedimentation From a H ydraulic Dredge in a Bay1 THOMAS R. HELLIER, JR.2 AND Loms S. KoRNICKER3 Abstract Red grave! was used to mark the hay sediment surface at 5 statíons in turtle grass flats neu Aransas Pass, Texas prior to the dredging of an intracoastal waterway. Cores were ta.ken and sedi-· ments were studied before, one week after dredging, and 18 months later. 22 to 27 cm of sediment (11 to S!i% silt-clay) were deposited within 0.5 mile of the dredge, but effects at greater distance were negligible. Little sediment sorting was observed during dredging. lntroduction lt is routine in the digging o·f channels in Texas hays and lagoons for a hydraulic dredge to deposit sediment removed from channels in discrete piles called "spoil islands" or "spoil hanks." The ohjective of the present study was to •ascertain the amount of sediment distrihuted on a shallow fertile hay hottom as a result of sediment hy-passing the spoil island during the dredging operation, and by lated erosion of the spoil islancl The work was part of a joint project by the Texas Game and Fish Commission of TCU!I, . and the lnstitute of Marine Science, designed to determine the effect of dredging on ·· marine life. The area chosen for the study was Redfish Bay, near Aransas Pass, Te~· A "hefore and after" type study was possihle hecause of a projected extension of ~· · intracoastal canal, 125 feet wide and 12 feet deep, through Redfish Bay. The method used to estímate the amount of sediment deposited in the hay by ~:­dredge was as follows: square meter quadrats were marker off in five locations over tll.j:''., turtle grass flats in Redfish Bay by setting a hamhoo pole, easily visible from a distance,:; at each comer of a quadrat. A layer of red aquarium gravel was then spread on top o(: the sediment inside the quadrats. Cores were then collected periodically hefore and after: dredging from within each quadrat, and the thickness of sediment ahove the red gravel measured. Plastic tuhes 1 % inches in diameter were used for coring. The five quadrats were oriented perpendicular to the proposed channel (Fig. 1). The channel was dug hetween quadrat 1 and the mainland. Quadrat 1 was approxi­matel y 0.03 mile from the channel, quadrat 2 was 0.5 mile, quadrat 3 was 1.0 mile, quadrat 4 was 1.5 miles, quadrat 5 was 2.0 miles distant from the channel. The spoil from the channel was deposited hetween quadrats 1 and 2, hut closer to 1 than 2. Results Cores ohtained immediately after the red gravel was spread on the sediment were kept in the lahoratory as controls in order to determine whether or not the gravel would sink by its own weight into the sediment. The gravel remained on top of the sediment 1 From a research problem in Mn. S. 380.3 Research in Marine Geology. 2 Supported by an inter-agency contract between the Texas Game and Fish Commission and the Institute of Marine Science; present address, Arlington State College, Arlington, Texas. 3 Present address, Department of Oceanography and Meteorology, A and M College of Texas, College Station. Sedimentation from a Hydraulic Dredge in a Bay F1c. 'l. Photograph facing south along the intracoastal channel after the dredging in May, 1960. Station 'l is indicated in the middle right. Station 2 is along the left margin. Stations 3-S, not visible, stretch out h> the left {west) of the spoil island more or less perpendicular to the channel axis. Dark areas underwater behind the spoil island are grass flats. The causeway between Aransas Pass and Port Aransas is visible in the backgmund. The narrow strip of land covered with vegetation in the foreground is man-made, once supporting a railroad. The picture was taken by Mr. W. Garner from a U. S. Army helicopter. in the coring tubes throughout the tests. Slight agitation simulating wave action in the tubes did not cause the grave] to sink in to the sediment. In September, 1959, nine months after the grave! was distributed, the quadrats were re-cored in order to estímate thickness of sediment deposited in the hay under existing conditions prior to dredging. The amount of sediment deposited during the nine month period was negligible at ali 5 quadrats, being at most 2-3 mm. The quadrats were again re-cored about one week after the dredge passed through the sample area. Twenty­seven cm of sediment were deposited over quadrat 1, and 22 cm over quadrat 2 (Table 1). Sediment deposited on quadrats 3, 4, and 5 was negligible. Eighteen months after the dredge had passed the sample area the quadrats were again Sedimentation from a Hydraulic Dredge in a Bay TABLE 1 Amount of sediment deposited before and after dredging• Tbickness of Station quadrat no . sedimenl deposited in 9 montbs prior lo dredgiog, cm Thickness of sedimenl 1 week afler dredging, cm Thickneu of sedimenl 18 montha afler dredging, cm 1 negligible 27 32 2 negligible 22 33 3 negligible Y:i negligible 4 negligible Y:i 5 negligible Y:i 3 • Thickness of sediment measured from reference surface marked with red gravel spread in December, 1958. re-cored in order to estimate the amount of sediment that had been distributed on the bottom as a result of erosion of the spoil island. The gravel in quadrat 1 was found to be covered with 32 cm of sediment and in quadrat 2 with 33 cm showing that 5 cm of sediment had been added to quadrat 1 and 11 to quadrat 2 as a result of erosion of the spoil island. Sedimentation on quadrat 3 was negligible; quadrat 4 could not be located. Quadrat 5 had 3 cm of organic muck over the grave!, but this apparently was not derived from the spoil island. In order to ascertain how the composition of the sediment was affected by dredging, the upper 10 cm of sediment in quadrats 1, 2, 4, and 5 were separated into a silt-clay and shell-sand fraction before the dredging by sieving (Table 2). The sieving was re- TABLE '2 Composition of sediment before and after dredging Miles Before dredging One week after dredging Stalion no. from dredge silt-clay per cent• sih-clay per cent• l 0.0'3 west 51 11 2 0.5 east 43 55 3 1.0 east 60 60 4 1.5 east -­ 5 2.0 east 67 67 * Remaining percenlage of sediment consisted of sand-shell fraclion. peated with the sediment deposited by the dredge in quadrats 1 and 2. The sediment deposited by the dredge in quadrat 1 was coarser than the original, containing only 11 per cent of silt-clay mixture compared to 45 per cent before dredging (Table 2). The sediment deposited on quadrat 2 was not appreciably different from the underlying sediment. The sediment deposited on quadrats 1 and 2 during the dredging operation was homogenous with no layers apparent. Sediment deposited during post-dredging erosion of the spoil island was finer than that deposited during the dredging (R. Schultz, personal communication, 1960). Discussion and Conclusions Ingle (1952) found after studying sediment deposition during dredging in a Florida hay that damage caused by deposition of mud on the bottom did not extend beyond 0.23 mile from the dredge. In Redfish Bay dredged sediment was deposited more than 0.5 mile, but less than 1 mile, from the spoil bank, somewhat further than Ingle observed in Florida. It might have been erroneously predicted that during the dredging operation dredged sand and shell would remain on or close to the spoil area, and clay and silt spread widely on the hay bottom. The similarity in the composition of sediment before and one week after dredging on quadrat 2 and non-deposition of sediment appreciably further than 0.5 mile from the spoil area indicate that the sediment was not sorted to an appreciable extent during the dredge operation. This may be because sediment containing clay is usually' ejected from the dredge ftume as chunks (mud halls) rather than as discrete particles (Kornicker, Oppenheimer, Conover, 1959) . Sorne sorting locally is indicated by the low percentage of the silt-clay fraction in sediment deposited on quadrat 1 dur­ing dredging. The accumulation of sediment finer than the original on quadrats 1 and 2 during the 18 months following the dredging indicates that sediment forming the spoil island is sorted as it is reworked by waves. lt might be predicted that sediment surrounding the spoil area will become somewhat coarser as the finer material is removed and distributed in deeper water. The fact that more sediment was deposited during the 18 month post-dredging period on quadrat 2 (11 cm) than on quadrat 1 (5 cm) suggests that waves are the principal agent eroding the spoil bank, since station 2 faces the windward side of the spoil island, whereas station 1 faces the lee side. The accumulation of more sediment on the windward side of the spoil island than on the lee side during the post-dredging period suggests that spoil islands formed during dredging should be situated on the windward side of channels from which the sediment was obtained in order to minimize the amount of sediment returning to the channel. The technique of using colored gravel chips as a reference to gauge deposition of sediment proved workable and may be useful for making similar studies elsewhere. Acknowledgments The authors wish to thank Mr. Frank Schlicht, Mr. Ray Childress, and Mr. Charles Wise for assistance in the field, and Dr. Donald W. Boyd for criticizing the manuscript. This study was in part supported by a Texas Game and Fish Commission Contract, No. 4413-347 with the lnstitute of Marine Science. Literature Cited Ingle, R. M. 1952. Studíes on the effect of dredgíng operations upon fish and shellfish. Tech. Ser. Fla. Bd. Conserv. 5: l-'26. Kornícker, Louis S., Car! H. Oppenheímer, and John T. Conover. 1959. Artíficíally formed mud halls. Pub!. lnst. Mar. Scí. Univ. Tex. 5(1958): 148-150. Shrimp Landings and Production of the State of Texas for the Period 1956-1959, with a Comparison with other Gulf Sta tes 1 2 GoRDON GuNTER Texas Game and Fish Commisswn Seabrook, Texas Abstract Data on shrimp production from 1956 through 1959 in Texas and other states of the Gulf and South Atlantic area are presented in tables and graphs from state and federal sources. lnterpretive comments are made on trends, seasonal variations, and areal differences. In Texas total production has been relatively stable but white shrimp production has declined. White s'hrimp dominate landings in Louisiana and the upper Texas coast; brown shrimp domínate the catch of the central Texas coast; while pink shrimp are important in Florida and the lower Texas coast. Fo.Jlowing maximum yields of brown shrimp in summer and white shrimp in the early fall, catch records show a southward drift of populations off the Texas coast in fa!!. Catch per hour was correlated with total production and was markedly seasonal. Introduction A few years ago the United States Fish and Wildlife Service introduced a better and more complete system of collecting production statistics on the shrimp fishery. This program was carried on in collaboration with the various states. These statistics and sorne earlier ones collected by the Texas Game and Fish Commission were utilized in this assessment of the present production of the shrimp fishery of Texas. The concern is with landings and production and not with price variations and other economic factors. The Marine Products Reports and previous annual statistics of the Texas Game and Fish Commission, which were used only briefly for comparison with former years, have been published in the various Annual Reports of the Game and Fish Commission ex· tending back for almost forty years. They are not cited. The federal figures used are from work sheets furnished by the Fish and Wildlife Service to the Marine Laboratory of the Game and Fish Commission at Rockport, Texas (Table 1). These differ slightly from the figures published in the annual Fishery· Statistics of the United States. Both sets of data are on file at Rockport. The following account refers to landings of the United States Gulf of Mexico coast, and more briefly to the south Atlantic coast. The minor Pacific coast shrimp fishery is not considered. 1 Contribution No. 54 from The Marine Lahoratory of the Texas Garne and Fish Commission. 2 Present Address: Gulf Coast Research Lahoratory, Ocean Springs, Mississippi. TABLE 1 Gulf shrimp landings in pounds, heads-off Yeor Florida Alabama Mississippi Louisiana Texas Grand total 1956 Brown 556,997 3,067,848 6,095,390 12,123,228 33,179,663 55,023,126 Pink 28,013,357 261,920 200,400 765 496,281 '28,972,723 White 617,399 1,249,9415 2,355,629 17 ,'131,580 3,135,661 24,490;214 Seabobs 47,433 250 828,647 79,442 95'5,772 Total 29,235,186 4,579,713 8,651,669 30,084,220 36,891,047 109,441,835 1957 Brown 707,137 2,993,847 5,673,824 l'l,120,068 43,136,212 63,631,088 Pink 23;155,810 188,302 354,302 46 138,908 '23,837,368 White 881,161 410,417 %7,084 6,581,743 2,298,533 11,128,938 'Seabobs 207,985 325;190 117,040 650,215 Total 24,952,093 3,592,566 6,985,210 18,CY27,047 45,690,69'3 99,247,609 1958 Brown 1,024,035 2,261,455 2,972,957 8,324,163 36,669,887 51,252,497 Pink 24,539,434 68,906 103,754 294,383 9,876 25,016,353 White 1,573,384 829,21'2 1,512,567 14,4154,824 7,369',827 25,739,814 Seabobs 9,919 845,672 243,2'14 'l,098,805 Total 27,1'46,772 3,159,573 4,589;278 23,919,042 44,292,804 10:>,107,469 1959 Brown 953,254 3,795,381 5;457,779 16,143,481 43,428,838 69,778,733 Pink 17 ,3'52,690 2,193 '168,900 1,495 937,968 18,463,246 White 755,230 974,276 1,894;19'2 15,172,218 5,761,192 24,557,108 Seabobs 136,82'2 476 375 2;037,796 178,270 2,353,739 Total 19,197,996 4,772,326 7,521,246 33,354,990 50,306,268 115,'152,826 Shrimp Landings of Texas and other Gulf States SHRIMP L ANDINGS AT UNITEo STATEs GuLF PoRTS During the years 1956 to 1959, inclusive, the United States Gulf landings of shrimp tails were 426,950,352 pounds. Shrimp with the heads off were multiplied by a factor of 1.68 to obtain the whole weight. The United States Gulf landings of whole shrimp dur­ing this four year period were 717,276,771 pounds. lt should be noted that these figures represent more than the total production of the Gulf states, for sorne of the shrimp were caught outside of territorial waters of the United States. Similarly, the figures are less than the total production figures for the Gulf of Mexico, for the figures on Gulf shrimp landed in Mexico and Cuba were not available. The United States landings during the same four year period, including the South Atlantic states, were about 820 million pounds in tenns of whole shrimp, with an aver­age of about 205 million pounds a year. The South Atlantic production comes from North and South Carolina, Georgia, and the Atlantic coast of Florida. Due to the high price of the product, the shrimp fishery was the most important one in the United States, exceeding any of the others in value, such as the menhaden fishery, although in 1956 and again in 1959 over two billion pounds of menhaden were landed. During the 1956-1959 period the Gulf landings of headed shrimp fluctuated from a low of 99 million pounds in 1957 to a high of ll5 million pounds in 1959, with an aver­age of slightly less than 107 million pounds a year. The figures are shown in Fig. l. L ANDINGS BY STATES The annual Texas landings of heads-off shrimp during the four year period varied from a little less than 37 million pounds in 1956 to over 50 million in 1959, with an Shrimp Landings and Productwn of the St,ate of Texas 100 V) ~ 80 :::. o o.. ... 60 o V) a 50 V) <:<: :::. o 40 ~ 40 o.. _, _, ~JO i 20 ~ 20 o ~ 10 :: ~ o 1956 1957 1958 1959 AVG. FIG. l. Total landings of headed shrimp at FIG. 2. Total landings of headed shrimp at United States Gulf Coast ports, 195.6-1959. Texas ports, 1956-1959. average of over 44 million pounds a year. Texas landings were 41.5 per cent of the Gulf landings during this period. The figures are given in Fig. 2. Table 1 shows the variations in landings of heads-off shrimp for the severa) Gulf States, with averages and percentages. Severa) interesting facts are apparent. The Texas shrimp fishery is larger than that of any other state in the Union. Texas, Louisiana and Florida are the states with high landings and 90 per cent of the Gulf Coast landings come into ports of these three states. The remaining 10 per cent goes into Mississippi and Alabama ports. Louisiana and Florida landings are almost equal, but Louisiana stands higher as a producer than is shown in the table, because a considerable propor· tion of the Mississippi and Alabama landings are caught in Louisiana waters. Further­more, a considerable proportion of Texas and Florida landings come from the Campeche Banks, but Louisiana landings come primarily from waters of that state. Among the high producing states, the Louisiana landings fluctuated most from the averages, 32.0 per cent, and Texas landings fluctuated least, 16.7 per cent. Florida landings fluctuated 23.6 from the mean. These facts are noted here because stability of landings is of great importance to the industry. Table 1 also shows that 1959 was the year of highest landings for Texas, Louisiana and Alabama and 1956 was the best year for Florida and Mississippi. Figure 3 shows graphically the average annual heads-off shrimp landings of the various Gulf states for the four year period. V) o <: 50 :::. o o.. 40 ... o 30 V) <: 20 ~ _, :: 10 TEX. LA. FLA, MISS. ALA. V) Cl <:: ::::. o !l. 60 40 .... o V) <:: !;? ..J :::!. 20 ~ F1G. 3. Average annual landings of headed FIG. 4. Average annual production of headed shrimp of the Gulf States, 1956-1959. Gulf shrimp by species, 1956-1959. LANDINGS BY SPECIES Four species of shrimp are fished commercially in the Gulf of Mexico. The annual average landings at Gulf ports in pounds of headed shrimp fo.r the four year period were: seab<>bs (Xiphopeneus kroyeri) 1,264,633 (1.2 per cent) ; white shrimp (Penaeus fluviatili,s) 21,479,019 (20.l per cent); pink shrimp (Penaeus duorarum) 24,072,423 (22.5 per cent); brown shrimp (Penaeus aztecus) 59,921,361 (56.2 per cent). These fig· ures are shown graphically in Fig. 4. During the period under discussion Mississippi and Alabama landed only 1,101 pounds of seabobs. Florida averaged 100,540 pounds, or 8.0 per cent of the Gulf landings; Texas averaged 154,492 pounds or 12.2 per cent, and Louisiana averaged 1,009,326 pounds, or 79.8 per cent of the annual Gulf catch of the species. In Texas the average seabob landings for the four-year period amounted to slightly more than 0.3 per cent of the state total of shrimp landings, and in Florida the percent· age was only 0.4. Actually, the seabob is of importance only to the State of Louisiana, where it amounted to 3.8 per cent of the total shrimp landings. In 1959, seabob landings were 6.1 per cent of the Louisiana total. Seabobs are generally caught in United States waters, but they are not of much importance to Texas, and make up only about 1.2 per cent of the Gulf landings for the four-year period. In 195~59 Florida landings of pink shrimp amounted to 23,265,323 pounds a year or 96.6 per cent of the Gulf pinks. Texas was second with 395,558 pounds a year or 1.6 per cent of the Gulf total. Mississippi, Alabama and Louisiana trailed in pink shrimp landings with less than 1.0 per cent each. The average annual landings for these three states were: 206,839, 130,330 and 74,172 pounds, respectively. Florida dominates the pink shrimp landings in the Gulf of Mexico and that shrimp is of little importance to the other states. The average annual landings for the period 195~59 of pink shrimp, white shrimp and brown shrimp are given by states in Table 2. Louisiana led in white shrimp landings and Texas led in brown shrimp landings. The white and brown shrimp are of little importance to Florida, but they are of major im· portance to the other Gulf states. Texas ranks first in landings of the browns and sec· TABLE 2 Annual average landings of heads-off pink, white and brown shrimp for ali Gulf states for the period 1956-59, inclusive, with percentages Pink shrimp Florida Texas Mississippi Alabama Louisiana Annual landings Gulf percentage 23,265,323 96.6 395,578 1.6 206,839 0.9 130,330 0.6 74,172 0.3 White shrimp Annual landings Gulf percentage Louisiana 13,335,091 62.0 Texas 4,64'1,303 Zl.6 Mississippi 1,679,868 7.8 Florida -956,794 4.5 Alabama --·· -865,963 4.0 Brown shrimp Texas Louisiana Mississippi Alabama Florida Annual landdings 39,103,675 11,927,735 S.,049,988 3,029,63'3 810,356 Gulf percentage 65.2 19.9 8.4 5.1 1.4 Shrimp Landings and Production of the State of Texas ond for each of the other three shrimp (seabobs, pinks and whites). Louisiana ranks first in landings of whites and seabobs, second in browns and last in pinks. The average annual shrimp landings in Texas by species are given in Table 3 with percentages of the State total. lt is clear that Texas shrimp problems are concerned mostly with the brown and white shrimp. TABLE 3 Average heads-off shrimp landings of Texas by species for the period 1956-1959 Annual landings Percentagc Brown shrimp 39,103,650 88.3 White shrimp 4,641,303 10.5 Pink shrimp 395,758 0.9 Seabobs 154,492 0.3 Total 44,295,203 Texas Shrimp Production Actual production figures of shrimp taken in Texas waters from 1956-59 ranged from 24,873,550 to 34,399,946 pounds of headed shrimp, and averaged 30,264,927 pounds annually. Table 4 shows that Texas produced an average of 68.3 per cent of the shrimp landed in the State, and 31-7 per cent or 14,030,003 pounds a y'ear carne from waters outside the State. TABLE 4 The average annual catch of headed shrimp in Texas water for the years 1956 to 1959, inclusive, compared to shrimp landed from out of state State waters Out of slale Ponnds Per cent Pounds Per cent Seabobs 359 0.2 154,133 99.8 Pinks 3'2,040 2.0 'l,550,993 98.0 Whites 4,118,210 88.7 523,093 11.3 Browns 26,114,318 66.8 12,989,357 '3l3.2 Total 30,264,927 68.3 14,030,003 31.7 lt is also clear from Table 4 that Texas waters produce few seabobs and few pinks, Probably the seabobs and white shrimp come from Louisiana waters, and the out of state browns and pinks from other waters of the western Gulf. Table 4 also shows that the brown and white shrimp make up 99.9 per cent of the Texas shrimp catch, the browns amounting to 86.3 per cent of the total and the whites amounting to 13.6 per cent. The average annual white shrimp production for this period was slightly less than 7 million pounds of whole shrimp. During the 1930's the annual shrimp production of Texas averaged 12.3 million pounds of whole shrimp-these were entirely white shrimp, which was the only species fished at that time. In the 1940's the white shrimp produc· tion averaged 18.3 million pounds a year. During the late 1940's the brown shrimp fishery was begun. In 1950 Texas produced 12.7 million pounds of whole white shrimp, but the next year the catch fe]] off, and for the years in which we have statistics ( 1951, 1952, 1956 to 1959) the average annual production of whole white shrimp was only 6.7 million pounds, about half what it was in the 1930's and slightly more than a third of what it was in the 1940's. There are several possible explanations of this decline in the white shrimp catch. For one thing, after the brown shrimp fishery got started in 1947 larger boats were built and the fishermen put more effort into Gulf fishing, which is in general devoted to the brown shrimp. They have never returned to hay fishing on the scale of the 1940's. How· ever, shrimp fishermen turned to brown shrimp because ·the white shrimp declined in parallel with the greatest drouth this country has ever known. This drouth began in 1947 and became worse in the 1950's and was not broken until the spring of 1957. 1t is interesting to note that the average annual production of white shrimp in 1958-59 jumped to 9,852,000 pounds of whole shrimp, as compared to 3,985,000 for the previous two years. The increase was about 125 per cent following the rains. The writer has previously shown that Texas shrimp production is correlated with rainfall of the State, especially that of the same year and the two previous years (Gunter & Hildebrand, 1954). However, there are other changes which tend to cause the decline in shrimp produc· tion shown in the statistics, especially in the bays where mostly white shrimp are caught. The relatively recent production of powerful outboard motors has led to the acquisition of hundreds of small cabin cruisers by sports fishermen. These people huy bait shrimp licenses and do their own trawling, not only for bait but for edible shrimp. The bait shrimp fishery has increased greatly, too, and these shrimp are not reported in the commercial catch. Chin (1960) showed that the two-year catch of bait in Galveston Bay amounted to 676,000 pounds. During the same period the commercial shrimp catch in Galveston Bay was 1,537,257 pounds. Not all of the shrimp reported were white shrimp, but the majority of them were. White shrimp production along the Texas coast has certainly fallen sharply in the past ten years, and the fishing for shrimp is probably as heavy as it ever was, and is increasing. These facts highlight the necessity for adequate information on the causes of the decline and laws to protect the shrimp. Texas Shrimp Catch by Areas The Texas coast was divided into four areas for the purpose of collecting statistics on shrimp catches. Area 18 extends from the Louisiana line to north of Freeport. lt in­cludes the area offshore from Galveston Bay. Area 19 includes the Gulf area south of Freeport and the waters offshore from San Antonio, Aransas, and Copano bays. Area 20 includes the area of Corpus Christi Bay and the upper Laguna Madre. Area 21 ex­tends outside the lower Laguna to Mexico. These areas are shown in Fig. 5. As was noted before, the seabob is produced primarily' in Louisiana waters. There­fore, it is not surprising to find that all but 12 pounds of the Texas seabob catch carne from Area 18, which borders Louisiana. The average catch for the whole coast was only 359 pounds ayear. Table 5 gives the average annual catch of pinks, white and brown shrimp for the four areas described above. Sixty per cent of the pink shrimp were taken from Area 20, which lies off Corpus Christi Bay and the upper Laguna Madre. Over eighty-two per cent of the white shrimp were taken from there, northward and eastward, to the Louisiana line in Areas 19 and 18. Brown shrimp were taken all along the coast but were caught Shrimp Landings and Productwn of the State of Texas Area 18 19 20 21 · Pink 4,947 4,657 19,2'23 '3,212 Whites 1,488,123 2,290,328 302,216 37,634 Browns 4,984,640 9,199,973 8;237,424 3,692,266 more than twice as abundantly in the two middle areas (19 and 20) as in the other two-the catch from these two areas being 66.2 per cent of the Texas total. Table 6 gives the average monthly catch of the whole coast for pink, white and brown shrimp. Almost half of the pink shrimp were taken in }une, and 94.3 per cent of the catch was taken in the months of April to July. TABLE 6 The average monthly production of heads-off shrimp by species of the Texas coast for the four year period, 1956-'1959. Figures are in pounds. Areas January Fehruary March April May June July Augui:t Septemher October Novemher Decemher Pinks 31 603 2,334 8,369 15,356 4,154 125 ... 697 308 65 Whites 11,380 2,181 23,05'1 84,466 249,421 66,233 42,356 319,275 1,405,323 1,202,032 525,771 186,190 Browns 556,046 430,212 377,514 341,742 588,012 1,430,524 4,722,558 5,742,581 5,136,878 4,159,394 1,707,868 921,031 Total 567,457 432,.393 401,168 428,542 845,802 l ,51'2,113 4°,769,068 6,061,981 6,542,201 5,362,123 2,233,947 1,107,286 TABl.f: 7 The average monthly production of heads-off white shrimp for the four areas of the Texas coast for the period, 1956-1959. Area11 Januury Fehruary March April Mny June July Au1rnst Seph'mhcr Ocl oht•r Novemb('t ))ecemher 18 3,743 1,876 7,203 15,1'16 26,431 24,623 9,802 65,5'0.3 513,502 570,740 216,901 32,183 19 6,396 240 14,259 63,619 176,979 29,771 29,114 237,676 774,12.) 573,415 265,549 119,150 20 627 65 1,575 5,140 38,132 9,475 3,436 16,096 106,217 57,774 37,760 25,922 21 615 o 14 590 7,879 2,.365 o o ll,481 103 5,562 8,936 Total 11 ,381 2,un 23,051 84,465 249,421 66,234 42,352 319,275 l ,405,.3'23 1,202,032 5·25,772 186,191 TABLF. 8 Monthly produr.tion of heads-off brown shrimp from the four statisiical areas from north to south. The figures are averages of the four years, 1956-1959. Arca~ January Fehruury March April May June July Augu.; t Seplemher October Novemher Decemher 18 3'1,902 27,954 22,401 21,138 37,639 210,367 l,205,296 1,425,423 709,476 1,046,588 196,736 49,715 19 125,054 60,616 106,012 103,814 270,664 359,449 1,524,638 2,301,824 l ,778,108 1,762,593 526,876 280,317 '20 223,648 204,900 141,816 121,4!17 166,794 698,410 l ,'231,140 1,590,739 1,762,659 1,014,850 695,146 374,946 21 175,439 136,741 107,283 95,373 101,908 162,297' 761,486 424,594 886,635 3'35,3'63 289,112 216,052 Total 556,043 430,21'1 377,514 341,742 588,012 l,430,52'3 4,722,560 5,742,.580 5,136,878 4,159',394 1,707,870 921,030 Shrimp Landings and Productwn o/ the State o/Texas September was the month of the greatest white shrimp catch and 63.3 per cent of the Texas catch was made during the months of September and October; 84 per cent of the catch fell in the four months of August to November. The only other month of siz. able production was May, which is apparently a reflection of the spring run that appears in sorne years. August was the month of greatest production of brown shrimp, and almost 74 per cent of the brown shrimp catch was in the months of July to October. When the total shrimp catch is considered it is seen that March and April are the months of lowest production, only 3.2 per cent of the annual total being taken in those months. In contrast ,40.0 per cent of the catch was taken during August and September, and 73.3 of the total catch was taken in the four months July to October. Table 7 shows the average white shrimp production by months for each area during the four·year period. February was the low month in ali areas. The spring increase in production began to show in March and reached a peak in May in each area. This is the well known "spring run" of the fishermen. Another interesting fact concerns the fall fishery. In every area, except 18, there was a decrease from September to October, and in ali areas there was a decrease from September to December, and the percentage decrease was less from north to south. The percentage declines from September to December for the four areas, 18, 19, 20 and 21 (from north to south) were 93.7, 84.6, 7S.4, and 22.3, respectively. The per· centage changes are even greater if we consider the period October to November. Dur­ ing that period, the trend reversed in the southernmost area and the catch increased from October to December. The percentage changes in catch for this period for the area from north to south are: -94.4, -79.1, -SS.O and 8,67S.O. The only reasonable explanation of this set of figures is that, after the shrimp go into the Gulf in the fall, they drift southward along the coast. Table 8 gives the average monthly production of brown shrimp for Texas by areas. The monthly variations in catches have already been discussed. The total production declined steadily from the high in August to the April low, but this decline was much less in the two southern areas from October to February. In October the two northern areas produced 67.S per cent of the brown shrimp taken on the Texas coast. In February, this figure was 20.6 per cent. These facts are clearly shown in Table 9. The trend was re- TABLE 9 The percentages of the total catch of brown shrimp of the two north and south areas by months, 1956-1959 Areas October :Xonmber December Januar~· February 18 and 19 67.5 .+2..t 35.8 28.2 20.6 19 and 20 32.5 57.6 64.2 71.8 79.4 versed in March. lt is clear that the brown shrimp population tends to drift southward down the Texas coast during the fall and winter. Unit of Effort and the Catch In addition to the production statistics from the various areas, the Fish and Wildlife Service workers have collected information by the interview method on days and hours fished, and the catch, in each of the four Texas areas during the years 1958 and 1959. These data cover 138,716 hours of trawling, which produced 3,974,923 pounds of headed shrimp. This is quite the most extensive data on this subject collected so far on the shrimp fishery. During the two-year period the boats on which the data were collected caught 28.7 pounds of shrimp per hour. In 1958 the catch was 26.2 pounds per hour; in 1959 it was 29.7 pounds. A comparison made with Table 1 shows that the shrimp catch increased in 1959 above the 1958 catch by 6,013,464 pounds, or 13.6 per cent. The catch per unit of effort increased 3.5 pounds per hour at the same time, or 13.2 per cent. The correspond­ence is remarkably close. This means that the increased catch in 1959 was due solely to better fishing and not to increased effort by the fishermen. The tables of data on catch and unit effort by months for each of the four years are quite bulky and will not be presented here. They are on file at the Marine Fisheries Di­vision office of the Game and Fish Commission at Rockport. Table 10 gives the two- TABLE 10 The monthly average of pounds of heads-off shrimp caught per hour for the years 1958 and '1959 (upper figure), with averages of the total catch for the same period Oower figure) , in millions of pounds January February March April May June July Augusl Seplember October November December 16.2 15.4 15.0 11.5 11.0 11.7 45.5 36.5 38.9 38.5 25.9 23.0 .436 .228 .278 .312 .609 1.427 5.456 6.709 7.084 5.912 2.077 1.066 year average catch of shrimp per hour each month for the whole Texas coast, in combi­nation with the total production. In general, there was strong correspondence between the unit of effort catch and the total catch. During the eight months from November to June, with a low catch of 941,000 pounds a month, the catch per hour of trawling was 16.2 pounds. During the high pro­duction months, with an average of 5,757,000 pounds production, the catch per hour of trawling was 39.8 pounds. Though the catch per hour of trawling decreased 60 per cent, the total catch decreased about 85 per cent in the low months as compared to the high months. If these data are typical of the whole fleet, as they are supposed to be, this means that the fishing effort decreases a great deal during the late fall , winter and spring months. The hourly catch of shrimp in pounds for each month and the total Texas production for the same months are shown graphically in Fig. 6. V) 6 Cl '1 ~ 5 Cl Q 4 "­ º .3 ¡ JFl.fA l-1 JJ ASONO Fu;. 6. The catch per hour of shrimp (solid line) compared to the total catch (dotted line) along the Texas Coas!. The figures are monthly averages for the years 1958-1959. Shrimp Landings and Productwn o/ the SUJt,e o/ Texas Summary l. The total landings of shrimp tails at United States Gulf Coast ports during the period 1956 to 1959, inclusive, was 426,950,352 pounds. During the same period the total landings of whole shrimp for the South Atlantic and Gulf states was approximately 205,000,000 pounds ayear. 2. During the 195~59 period, Gulf landings of headed shrimp ffuctuated hetween 99 and 115 million pounds with a yearly average of slightly less than 107 million pounds. 3. In terms of per cent of total landings, the rank of the Gulf states for the four-year period was: Texas 41.5, Louisiana 24.7, Florida 23.6, Mississippi 6.5, Alabama 3.8. Of the three top states, the annual ffuctuation in per cent was: Louisiana 32.0, Florida 23.6 and Texas 16.7. Texas has the most stable industry. Texas landings varied from 37 to 50 million during the period and averaged 44,295,000 pounds ayear. 4. The Gulf landings by species consisted of seabohs ( 1.2 per cent) , white shrimp (20.1), pink shrimp (22.5) and brown shrimp (56.2). Florida led in pink shrimp landings and Louisiana led in white shrimp and seabob landings. Texas led in hrown shrimp landings and was second in landings of the other three species. 5. Texas production of heads-off shrimp for the four year period averaged 30,264,927 million pounds annually; 14,030,003 pounds, or 31.7 per cent of the landings, carne from out of the state. 6. Texas annual production averaged 26,114,000 pounds of hrown shrimp, 4,118,000 pounds of whites, 32,000 pounds of pinks and 359 pounds of seahobs. 7. During the 1930's Texas production of white shrimp averaged 12.3 million pounds of whole shrimp. During the 1940's the comparable figure was 18.3 million pounds. During the 1950's the production was only 6.7 million pounds. The decline in white shrimp production during the past ten years has been over 63 per cent. 8. The Texas coast was divided into four areas, from the Sabine to the Rio Grande. Most of the pink shrimp catch is taken off Corpus Christi Bay. Most white shrimp are taken in the two easternmost areas. The greatest brown shrimp production is from the two middle areas, Freeport south to Aransas Pass. 9. September is the peak month for production of white shrimp. August is the peak month for hrown shrimp production. Over 73.0 per cent of the Texas shrimp catch is made during the four months July to October. 10. The total catch of white and brown shrimp declines from the peak months on into the winter, but the percentage decline is less and less southward clown the coasL This means that both white and brown shrimp move southward, clown the Texas coast during the winter. 11. During the years 1958 and 1959, Texas shrimp boats caught an average of 28-7 pounds of headed shrimp an hour. In general the catch per hour rose and fell with the total production, but the percentage of production fell much greater in the eight low months of the year than the catch per hour. Literature Cited Chin, Edward. 1960. The bait shrimp fishery of Galveswn Bay, Texas. Trans. Amer. Fish. Soc. 89(2): 135--14:1. Gunter, Gordon and Henry H. Hildebrand. 1954. The relation of total rainfall of the State and catch of the marine shrimp (Penaeus setiferus) in Texas waters. Bull. Mar. Sci. Gulf Carib. 4(2): %-103. Marine Algae From the Gulf Coast of Texas and Mexico H. J. HUMM1 Department of Botany Duke University, Durham, N. C. AND H. H. HILDEBRAND2 Department of Biology University of Corpus Christi Corpus Christi, Texas Contents Page INTRODUCTION -----------------------------------------------------------------------------------------··· ······-----·-227 ANNOTATED LIST OF SPECIES Cy'anophyta ---------------------------------------------------------------------------·. _,_________ ._ ______________ . 234 Chlorophyta 237 Chrysophyta 244 Phaeophyta ---------------------------------------------------------------------------------------___ ._..___._________ 244 Rhodophyta ----------------------------------------------------------------------------------------._______ ._________ . 249 SUMMARY AND COMMENTS -------------------------------------------------------------------------------------------261 LITERATURE CITED 262 Abstract An annotated list of 193 species of marine algae is given as a result of collections made along the coast of the Gulf of Mexico between Rockport, Texas, and the southern part of the State of Vera Cruz, Mexico. One hundred and sixteen of these species were recorded for Texas and '1'40 for Mexico. The greater number from Mexico is indicative of a richer flora rather than more thorough collecting. South of the Rio Grande, especially along the coast of Vera Cruz and southward, there is an abun­dance of favorable substrata and warmer inshore water during winter. The algae listed here represent only a portion of the many collections yet to be studied. lntroduction Very little is known about the distribution of the marine algae around the shores of the Gulf of Mexico with the exception of the Dry Tortugas area, intensively studied by Taylor (1928). From Everglades, Florida, northward and around the entire Gulf coast to Cuba, our information is spotty and sparse. 1 Aided by a summer stipend for regional systematics of the western Gulf from the lnstitute of Marine Science in 1957. 2 Visiting Re.search Program, lnstitute of Marine 'Science. Marine Algae /rom the Gul/ Coast o/ Texas and Mexico Taylor (1935a, 1940, 1941) reported and summarized the records of Texas algae, the present published total of which is now about 60 species. The east coast of Mexico figured early in marine botanical üterature of the New World as a result of collections made in 1845 by ·Prof. Frederik C. Liebmann of the l"niversity of Copenhagen, botanical explorer and describer of many new species of land plants of Mexico. Liebmann sent his collections of algae to J. G. Agardh of Lund, Sweden, who publi.shed on them in 1847. In this list of 29 were about 10 species from the State of Vera Cruz and Campeche Banks of the Mexican east coast the type localities for seYeral of them. Additional records from the Gulf coast to Mexico were noted by Taylor (1935h, 19.:tl), adding about 45 species to the lisL and by Humm 11952, 1956) whose list of 2-l from Campeche Banks included 12 not previously reported. Taylor (1954-a. 195-lb) summarized the scant knowledge of the algae of the Gulf of Mexico and their known distribution and discussed the nature of the coastline and alga! habitats. TEXAS ALGAL CoLLECTio:-;s The coast of Texas is a broadly embayed deltaic coastal plain l Price 1954) with about 400 miles of sand beach, many barrier island.s and extensive salt and brackish marshes. There are no natural rocks, other than oyster reek so that this is one of the principal reasons that the marine algae are limited in abundance. The United States Army Corps of Engineers, however. has constructed fiw pair.s of rubblestone jetties within the past 75 years in order to maintain naYigability into the passes of Sahine, Bolivar (Galves­ton), Freeport Aransas, and Brazos Santiago. These jetties proYide an ideal substratum for algae and thus permit the development of a flora adapted to the other environmental conditions of the area. The Aransas Pass and Brazos Santiago jetties have been the principal source of Texas algae with which this paper is concerned. The three sets of jetties to the north haw yet to be studied. In addition to the jetties, collections were also made in Texas at the following loca­ tions: in the southern end of Copano Bay at Rattlesnake Point; along the seawall at Rockport, Aransas Bay; in Redfish Bay, a subdivision of Aransas Bay near the town of Aransas Pass: around Harbor lsland in Aransas Bay; at Cline Point near Port Ar· ansas; in the Laguna Madre bet:ween Corpus Christi Bay and Port Isabel, especially at channel marker 69, al the Arroyo Colorado cut-off. at flasher 89, in Baffin Bay, Port Mansfield Harbor. and from buoys 119, 129, and 138 near or in the harbor of Port Isa­ bel. The Texas collecting station;; li.sted abow are .shown on the map in Fig. l. The geological nature. hydrography. and other enYironmental features of the Texas coast have been described in considerable detail by severa! author.s. most of whom ha,·e worked at the In.stitute of Marine Sciences at Port Aran.sas. Hedgpeth (1948) studied the Laguna Madre of Texas. Collier and Hedgpeth (1950't made a thorough study of the hydrography of the tidal waters of Texas. Additional information and data on the environment are to be found in papers by \Vhitten et al. (1950), Ladd (1951), and Hedgpeth ( 19531. The mean tidal range along the Texas coa.si is u:mally 1.5 to 2 feet with spring tide extremes of three feet in many places (Aran.sa.s Pass and Brazos Santiago jetties, for example:1. Marine Algae from the Gulf Coast o/ Texas and Mexico ... ... ... ... ... ... -· FIG. l. The western Gulf of Mexico showing the Texas collecting areas and the principal localities of the Mexican collections. Frorn 1949 to early 1957, when drought conditions prevailed over south Texas, the average salinity of Copano Bay was above 20 %o (Parker 1955). The salinity of Copano Bay is also influenced by the drainage of brine frorn old oíl fields into the Aransas and Mission rivers. AH algae collected in Copano Bay in connection with the present work carne frorn water with a salinity of 18 %o or above. In Aransas Bay·, the usual annual salinity range of bottorn water is between 15 and 25%o. In the Laguna Madre, salinities occasionally becorne extrernely high, sometimes ex­ceeding 100 %o· These great fluctuations result in mass mortalities of animals and plants, followed by reinvasion when suitable conditions return. During the 1950's, salinities in the Laguna Madre were consistently lower, according to Simmons (1957), than dur­ing the period studied by Hedgpeth (1948). Hildebrand and Markey (unpublished manuscript) attribute this to a fortuitous distribution of heavy rainfall on the water­shed, and to improved circulation in sorne areas because of navigational canals. Water temperatures in Aransas Bay usually exhibit an annual range of from 13 to 30ºC. The portion of the Aransas Pass jetty below the low tide level is subjected to a slightly narrower range than this. Data on salinity, water temperature, light penetration, and other marine environ­ Marine Algae from the Gulf Coast o/ Texas anti Mexico mental factors are of very limited value in understanding the influence of these factors upon the distribution of marine algae unless these data are obtained in direct relation­ship with the presence of the various species in a given area. Species of marine algae often appear and disappear in relation to environmental fac­tors other than the annual temperature changes, and they are able to survive short periods of potentially lethal conditions. The actual range of tolerance of the marine algae to fluctuating salinity, temperature, and light intensity is known for a very few, and the interrelations of these and other environmental factors is unknown for macroscopic algae. MEXICAN COLLECTIONS The collections from Mexico with which this paper is concerned carne from three general areas: the Laguna Madre of Mexico along the coast of the state of Tamaulipas at Boca Jesus Maria and Punta Piedras; in the northern part of the state of Vera Cruz in Laguna de Tamiahua and at Cabo Rojo; and from the environs of the city of Vera Cruz in the southern part of the State, southward about 15 miles to the town of Anton Lizardo and the nearby reefs (Blanca and Giote,I. The majority of the Mexican records listed carne f rom within a three-mile radius of the harbor of Vera Cruz. Fig. 2 shows the coastal area of Tamaulipas from the Rio Grande to Tampico and the entire Laguna Madre of Mexico. Fig. 3 shows the Punta Piedras area of the La,,,uuna and Boca Jesus Maria pass, the two localities from which collections were obtained. The outer coast of Tamaulipas is a sandy, high-energy shore like that of Texas and is without rocky outcrops. The Laguna Madre is the largest coastal lagoon in the state. Hildebrand (1958) summarized the available information on the hydrography and fauna of this area. He concluded, on the basis of scanty data, that the entire lagoon was hypersaline throughout the drought years of the 1950's. The northernmost 50 kilo­meters were classified as a brine pool too salty for fish life, although he noted that this area has passed through severa] productive and nonproductiYe cycles since commercial fishing started there in 1911. No macroscopic algae were observed in the northern sector of the lagoon. Ali collec­tions carne from the Boca Jesus Maria and Punta Piedras localities. Punta Piedras (Point of Rocks) is under the influence of tidal currents and COJL"t'<)Uent water exchange through Boca Jesus Maria (Eighth Pass) so that the salinity here does not become too high for euryhaline species of marine algae. Local reports indicate that the rainfaU is higher here than elsewhere in the Laguna because of the Sierra San Carlos to the west­ward. Five miles south of Boca Jesus Maria. along the west shore of the barrier islaod and at Punta Algodon (South Point of Rocks), the salinity wa.s 41 º~< at the time col­lections were made on October 22 and 23, 1953. At Punta Piedras on March 19, 1954.., salinities of 44 and 46 %o were recorded. Laguna de Tamiahua. The Laguna de Tamiahua (Fig. 4 and 5 t is the largest coastal lagoon of the state of Vera Cruz. The main body of water is approximately 60 miles long and has a maximum width of 25 miles. Most of the lagoon, however, is much nar­rowed and its surface area is further reduced by a number of islands. It is separated from the Gulf of Mexico by a barrier island, Cabo Rojo, which was a peninsula before the construction of the Chijol canal. DeBuen (1957) has published the only hydrographic description of the area. He occupied 16 stations between December 20 and 23, 1955. The lagoon is apparently Marine Algae from the Gulf Coast o/ Texas and Mexico MAP of PUNTA PIEDRAS and BOCA JESUS MARIA loJesus Mario CO ASTAL WATfRS TAMAULIPAS , MEfüO 97º 30' 1 F1G. 2. Collecting stations along the coast o( Mexico between the Río Grande and Tam­pico. very shallow, and ali his station depths are given as less than two meters except for one reported as 3.2 meters west of Isla Juana Ramirez. He found muddy bottom in the deeper central area and muddy sand, sand, or sand mixed with shell along the edges. DeBuen's salinity determinations were made after one of the most disastrous hurri­cane seasons ever to strike this portion of the Mexican coast, and about two and a half months after a record flood crest of the Rio Panuco at Tampico on October 5, 1955. In the Laguna north of Isla Toro he recorded salinities of 2.54 to 3.42 lfo0• At the time the algal collections were made, a number of surface salinities were re­corded from Yarious parts of the Laguna de Tamiahua in December 1953 and 1954 and in April 1955. These ranged from 4.94 to 12.13 %,c. Additional surface salinity de­terminations were made for a linear series of 11 stations from the northern entrance of the intracoastal canal to Isla Martinica on April 28-29, 1955. The range was from 18.23 %o on the north to 9. 75 %o at Isla Martinica. As pointed out by DeBuen, the primary factors which control salinity in the Laguna are rainfall and runo:ff, since connections to the sea are tenuous. In this region there are pronounced rainy and dry seasons. The rainy season normally occurs from the end of June to the end of October, although there is considerable yearly variation. During the rainy season the leve! of the Laguna may rise more than a meter and remain high for days. DeBuen (1957) reports a rise of 1.30 meters during the 1955 hurricane. Marine Algae from the Gulf Coast o/ Texas and Mexico VERA CRUZ Slatule M i/es · Pvnld JJnh;n l iJardo (' i /v arado Talt.#'n t'r oM ~ NATIO...iAL ú(06RAP\.llC MA.P j ~ Coat¡uoalt. CI. ~: 75-104. -----. 1914. The marine algae of Peru. Mem. Torrey bot. Cl.15: 1....1185. ----. 1915. Report on a visit to Puerto Rico for collecting marine algae. J. N.Y. bot. Gdn. 16: 219-2'25. ----. ·1918. Algae, p. 489-'540. In N. L. Britton, Flora of Bermuda. Chas. Schribner's Sons, New York. ----. 1920. Algae, p. 553-626. In N. L. Britton and C. F. Millspaugh, The Bahama Flora. Pub!. by the authors. Hoyt, W. D. 1917-1918. Marine algae of Beaufort, N. C., and adjacent regions. Bull. Bur. Fish., u. s. 36: 367-556. Humm, H. J. 1952. Marine algae from Campeche Banks. Florida State U ni v. Stud. 7 :27. ----. 1956. Rediscovery of Anadyomene menziesii, a deep water green alga from the Gulf of Mexico. Bull. Mar. Sci. Gulf Carib. 4: 346-348. Humm, J. J., and R. L. Caylor. 1957. The summer marine flora of Mississippi Sound. Pub!. Inst. Mar. Sci. Univ. Tex. 4('2): 228-264. Humm, H. J., and R. M. Dame!!. 1959. A collection of marine algae from the Chandeleur Islands. Pub!. Inst. Mar. Sci. Univ. Tex. 6: 265-276. Humm, H. J., and 'Sylvia E. Taylor. 1961. Marine Chlorophyta of the upper west coast of Florida. Bull. Mar. Sci. Gulf Carib. 11 (3): 3121-380. Joly, A. B. 1957. Contribuciio ao conhecimento da flora ficologica marinha da Baia de Santos e Arredores. Boletim 17, Botanica 14, Fac. de Philos., Cien. e Let., Univ. de Sao Paulo, Brasil. 99 p. Kjellman, F. R. 1900. Om Florides-slagtet Galaxaura, des organografi och systematik. Svenska Vet. -Akad. Handl., 'Ser. 4, 33(1): 1-109. Kuntze, O. 1898. Revisio generum plantarum vascularium atque cellularium multarum secundum leges nomenclaturae internationales cum enumeratione plantarum exoticarum in itinere mundi collectarum. Part 3. p. 1-576. Kützing, F. T. '1841. Uber Ceramium Agardh. Linnaea 16: 727-746. ----. 18'43. Phycologia Generalis. 1-XXXII, 1-456, 80 pi. Leipsig. Marine Algae from the Gulf Coast of Texas and Mexico -------.. 1845. Phycologica Gennanica. i-x, 1-240. Nordhausen. ----. 1845--1811. Tabulae Phycologiceae. Vols. 1-19 and index, 1'200 pi. Nordhausen. ----. 1847. Diagnosen und Bemerkungen zu neuen oder kritischen Algen. Bot. Zeit. 5: 52-55. ----. 1849. Species Algarum. i-vi, 1-922. Leipsig. Kylin, H. 1930. Entwickslungsgeschichte der Florideen. Lunds Univ. Ársskrift, N. F. Avd. 2, 26(6): 1-104. ----. 1933. Uber die Entwickslungsgeschichte der Phaeophyceen. Lunds Univ. Ársskrift, N. F. Avd. 2, 27(7): 1-102. ----. 1938. Uber die Chlorophyceengattungen Entocladia, Epicladia und Ectochaete. Bot. Notiser 1938 (l'/3 ): 67-76. ----. 194{). Die Phaeophyceenordnung Chordariales. Lunds Univ. Ársskrift, N. F. Avd. 2, 36(9): 1--07. ----. 1944. Die Rhodophyceen der schwedischen Westkuste. Lunds Univ. Ársskrift, N. F. Avd. 2, 4{)('2): 1-104. ----.1947. Die Phaeophyceen der &chwedischen Westkuste. Lunds Univ. Arsskrift, N. F. Avd. '2, 43('4) : 1-99. ----.. 1949. Die Chlorophyceen der schwedischen Westkuste. Lunds Univ. Ársskrift, N. F. Avd. '2, 45(4): 1-79. ----. 1956. Die Gattungen der Rhodophyceen. i-xv, 1--073. Ladd, H. S. 1951. Brackish water and marine assemblages of the Texas coast, with special reference to molluscs. Pub!. lnst. Mar. Sci. Univ. Tex. 2(1): 125--163. Lagerheim, G. '1'886. Note sur le Mastigocoleus, noveau genre des Algues marines de l'ordre des Phycochromacees. Notarisia 1: 65--09. Lamarck, J. P. R. de. 1813. Sur les polypiers empates. Ann Mus. Nat. Hist. '20: 294-312. Lamouroux, J. V. F. 1809a. Memoire sur trois nouveaux genres de la famille des algues marines, Dictyopteris, Amansia, Bryopsis. Jour. de Bot. (Redigé) 2: 1'29-1'35. ----. 1809b. Exposition des caracteres du genre Dictyota, et tableau des expeces qu'il ren­forme. Jour. de Bot. ( Redigé) 2: 38-414. ----. 1812. Sur la classification des polypiers coralligenes non entierement pierreux. Nouveau Bull. des Sci. par la Soc. Philom. de París 3: 181-188. ----. 1813. Essai sur les genres de la famille des thalassiophytes non articulees. Ann. Mus. d'Hist. Nat. (París ( '20: '21-47, l'lS-139, 267-293, pis. 7-13. ----. 1816. Histoire des polypiers coralligenes flexibles, vulgairement nomes Zoophytes. Caen. SóO p. Le Jolis, A. 1863. Liste des algues marines de Cherbourg. Mem. Soc. Sci. Nat. de Cherbourg 10: l-'168. Lund, S. 1950. The marine algae of Denmark. 11. Phaeophyceae. Kgl. Danske Vidensk. Selsk., Biol. Skrift. 6('2): 1-80. Lyngbye, H. C. 1819. Tentamen hydrophytologiae Danicae. !-XXXII, l-'240, 70 pi. Hafniae. Mackey, J. T. 1836. Flora Hibernica, comprising the flowering plants, ferns, Characeae, Musci, Hepaticae, Lichenes and Algae of lreland. 2 vols. Dublin. Mazoyer, G. 1938. Les Ceramiees de I'Afrique du Nord. Bull. 'Soc. d'Hist. Nat. Afrique du nord 29: 317-331. Mazza, A. 1905--1911. Saggio de Algologica Oceanica. Vol. 1, 1-528. Padova. Meneghini, G. 1842. Alghe italiane e dalmatiche. Fase. 1-V, 1-384, 5 pi. Padua. Meyen, J. 1838. Jahres'bericht uber die Resultate der Arbeiten im Felde der physiologischen Botanik von dem Jahre 1837. Archiv. fur Naturgeschichte 4(2): 1-186. Montagne, C. 1837. Centurie de plantes cellulaires exotiques nouvelles. Ann. de Sci. Nat., Bot., Ser. 2, 8: 345--370. ----. 184ü. Second centurie de plantes cellulaires exotiques nouvelles. Ann. de Sci. Na~.• Bot., Ser. 2, 13: 193-207. ----. 1846. Algues. In Exploration scientifique de l'Algerie pendant 184ü-4'2. Botanique. Tome I, Cryptogamie. Paris. 631 p. ----.1850. Cryptogamia Guayanensis. Ann. Sci. Nat., Bot., Ser. 3, 1'4: 281-309. ----. 1856. 'Sylloge generum specierumque plantarum cryptogamarum. París. 498 p. ----. 1860. Neuvieme centurie de plantes cellulaires nouvelles. Ann. Sci. Nat., Bot., Ser. 4, 14: 167-185. Marine Algae from the Gutf Coast o/ Texas and Mexico Moore, D. R. 1958. Notes on Blanquilla Reef, the most northerly coral formation in the western Gulf of Mexico. Pub!. lnst. Mar. Sci. Univ. Tex. 5: '151-15\5. Murray, G. 11188--1889. Catalogue of marine algae of the West lndian region. Jour. Bo~. 26: 193-196, 237-243, 303-307, 331-338, 358--363; 27: 237-242, 257-262, 298-305. Nageli, C. W. von. 1846. Polysiphonia and Herposiphonia. Schleiden und Nageli, Zeitschrift fur Microscopie, Heft 3. Newton, Lily. 1931'. Handhook of British Seaweeds. British Museum, London... 478 p. Nardo, l. 183'4. De novo genere algarum cui nomen ist Hildenbrandtia prototypus Isis, von Oken. 1834: 675--676. Oersted, A. S. 18412. Beretning om en Excursion ti! Trindelen, ·alluvial Dannelse i Odensfjord. Nat. Tidskrift 17: 552--568. Papenfuss, G. F. 1951. Problems in the classification of marine algae. Svensk Bot. Tidskrift 451(1): 4-11. Parker, R. H. 195\5. Changes in the invertebrate fauna, aparently attributable to salinity changes, in the bays of central Texas. J. Paleont. 29(2): 193-211. Phillips, R. C., and V. G. Springer. 1960. Observations on the offshore benthic flora in the Gulf of Mexico off Pinellas County, Florida. Amer. Mid. Nat. 64: 36'2-381. Price, W. A. 1954. Shorelines and coasts of the Gulf of Mexico. In Gulf of Mexico, its origin, waters and marine lifo. Fish. Bull., U. S. 55: 39--66. Rabenhorst, L. 1863. Kryptogamen-Flora von Sachsen. Algen. i-xx, 1-295. Leipsig. ----. 1865. Flora Europaea Algarum aquae dulcis et submarinae. Sec. II. Algas Phyco­chromaceas complectens. 1-319. Leipsig. Rayss, T. 1955. Les algues marines des cotes Palestiniennes. l. Chlorophyceae. Bull. 9, Sea Fisheries Res. Sta., Haifa, Israel, p. 1-36. Reinke, J. 1879. Zwei parasitischen Algen. Bot. ZeiL 37: 473-478. Rosanoff, S. 1866. Recherches anatomique sur les Melobesiees. 1-117, 7 pi., París. Rosenvinge, L. K. 1909. The marine algae of Denmark. Part l. lntroductio1'. Rhodophyceae l. -10 3 o o o 20-40 4 o 6 + 30 o Nitzschia seriata Cleve 1 2 o o 12 o 23 o o 0-18 0-8 o 0-15 3 4 o 23!>-247 17-187 55 20 o o o o 6-66 Scenedesmus sp. Meyen Chilomonas marina 2 2 3 4 o '23!>-247 82--131 6--'100 3-33 55 o o 20 o o o o o o o o o • Note : ""O" indicalea lhal area wa1 umpled bul no celh of the 1pecies were found . 0 .... " indicate1 that area wa1 not 1arnpled during lhal 1ea1ou . .. + •• indicateti that celh were present in concenlrations of leH than l/ml. TABLE 2 Minor phytoplankton species of the eastem Mississippi Delta Species SeasonB Areaa found, CI. %o M elosira monüi/ormis (Muller) Agardh M. islandica O. Muller M. ambigua (Grunow) Muller Stephanopyxis palmeriana (Greville) Grunow S. turris (Greville and Arnott) Ralfs Coscinosira polychorda Gran Thalassiosira rotula Muenier T. decipiens (Grunow) Jorgensen Cyclotella antiqua W. 'Smith C. bodanica Eulenstein Coscinodiscus lineatus Grunow C. curvisettus' Grunow C. margi'rtatas Ehrenberg . " C. granii Cough C. concinnus W. Smith C. centralis Ehrenberg C. oculus iridis Ehrenberg Actinoptychus undulatus (Bailey) Ralfs A. splendens (Shadbolt) Ralfs Asteromphalus heptactis (Brebisson) Ralfs Lauderia borealis Gran Schroderella delicatula (H. Peragallo) Leptocylinderus danicus Cleve Guinardia flaccida (Castercane) H. Peragallo Rhizosolenia stolterforthi H. Peragallo February, May February, May February, May May, November October May September September, May May February, May February, May September, November February, May September, November May Ali February, September May May May May February Plum e Plum e Plume, 1.54--2.92 Gulf Plum e Gulf Plume Plume, Blind Bay Gulf Plume, Gulf Gulf, 14.0-'17.0 Gulf, 14.0.-:17.0 Gulf Gulf, Breton Sound Gulf Gulf Gulf Gulf Gulf Gulf near Plume TABLE 2-Continued Minor phytoplankton species of the eastem Mississippi Delta Species Seasons Areas found, CI. %c R. robusta Norman R. imbricata Brightwell R. styli/ormis Brightwell R. calcar avis M. Schultze R. alata Brightwell R. acuminata (H. Peragallo) Gran R. setigerra Brightwell Bacteriastrum delicatulum Cleve B. hyalinum Lauder B. cumosum Pauillard Chaetoceros concavicornis Mangin C. van Heurkii Gran C. decipiens Cleve C. convolutus Castercane C. peruvianus Brightwell C. decipiens form singularis Gran C. teres Cleve C. constrictus Gran C. affinis var willei (Gran) Hustedt C. lacinosus Schutt C. laevis Leuduger-Fortmorel C. messanensis Castercane C. similis Cleve C. curvisettus Cleve C. pseudocurvisettus Mangin C. socialis Lauder C. gracillis Schutt May, 1957 netsamples February, May, October October May May May May September May, September May May May May February, May May June 1955 May 1957 February 1956 May 1957 February 1956-1957 February, May May 1957 Gulf, 13.0-19.0 Gulf Gulf Gulf, net sample Gulf Plume, Gulf Gulf Gulf, Breton Sound Gulf Gulf Gulf Gulf Breton Sound, Gulf Gulf Gulf Gulf Breton Sound Gulf Breton Sound, Plume Plume, Breton Sound Gulf TABLE 2-Continued Minor phytoplankton species of the eastern Mississippi Delta Species Seasons Areas found, Cl. %o C. vistulae Apstein Eucampia cornuta (Cleve) Grunow Ditylum brightwellii (West) Grunow Lithodesmium undulatum Ehrenberg Triceratium broeckii Leuduger-Fortmorel Bidulphia mobiliensis Bailey B. aurita (Lyngbye) Brebisson and Godey B. rhombus (Ehrenberg) W. Smith B. dubia (Brightwell) Cleve Hemiaulus hauchii Grunow Tabellarii sp. Ehrenberg T. fenestrata (Lyngbye) Kutzing T. fenestrata var. asterionelloides Grunow Diatoma elongatum Agardh Striatella delicatula (Kutzing) Grunow Grammatophora marina Ehrenberg C. oceanica (Ehrenberg) Grunow Licmophora abbreviata Agardh Climacosphenia moniligera Ehrenberg Campylosira cymbelli/ormis (A. Schmidt) Grunow Fragilaria sp. Lyngbye F. crotanensis Kitton Synedra sp. Bailey S. ulna (Nitzsch) Ehrenberg S . actinastroides Lemmerman Thallassiothrix longissima Cleve and Grunow May 1957 May net samples May netsamples October 1955 February 1956 February 1957 October, February, May November, February, Ma-y February 1956 February 1956, May Ali seasons February 1957 May 1957 May 1957 February 1957 May 1957 February, May, September May 1957 May 1957 May 1957 February 1957 February, May, September February, May, September February, May May 1957 May, September May, November Gulf Gulf Gulf Breton Sound Breton Sound Plume, near Breton Island Gulf, Breton Sound, 10.~16.0 Plume, Gulf, Breton Sound Breton Sound Plume, Gulf Plume, Gulf, Breton Sound Blind Bay, 0.4 Gulf Gulf River Gulf Gulf, near river Gulf net samples Plum e Gulf net samples Plume Ali areas, ~19.0 Ali areas, ~19.0 Plume, river, ~7.0 Gulf net samples Gulf, near plume Gulf, near Main Pass TABLE 2-Continued Minor phytoplankton species of the eastern Mississippi Delta Species Seasons Areas found, CI. %c T. mediterranea var. Pacifica Cupp T. delicatula Cupp Pseudoeunotia Grunow P. doliolus (Wallich) Grunow Cocconeis sp. (Ehrenberg) C. diminuta C. placentula (Ehrenberg) Navicula membranacea Cleve N. simplex Krackbe Gyrosigma spencerü (Quekett) Cleve Pleurosigma sp. W. Smith P. normanii Ralfs P. elongatum W. Smith Caloneis sp. Cleve N edium a/fine Pfitzer Diploneis sp. Ehrenberg D. interrupta (Kutzing) Cleve Stauroneis anceps Ehrenberg Amphipleura sp. Kutzing Pinnularia sp. Ehrenberg P. viridis (Nitzschia) Ehrenberg Amphiphora gigantea var. sulcata (O'Meara) Cleve Comphonema vibra Agardh Cymbella sp. Agardh C. lanceolata Ephithemia sp. de Bribisson E. zebra (Ehrenberg) Kutzing Nitzschia pungens var. Atlantica Cleve Ali seasons (May) February, 1956---57 May May 1957 .. May, September, October September 1956 February 1957 May 1957 May 1957 February 1957 February, May February '1957, May February 'l957, May May1957 February, September Ali seasons February 1957 February, May, September February 1956 February 1957 May 1957 February 1957 February 1957, May February 1957, May February 1957, May February 1957, May May 1957 Gulf Gulf, near plume Plume, near river Gulf Gulf, near Pass-a-Loutre Plume Gulf net samples Plume Plume River, Gulf Plume, Gulf Plume, Gulf River, 0-0.6 River, Blind Bay, 0-2.0 River, Plume Plume River, Plume, 0-6.0 River, 0-0.8 Plum e Plume River, 0-0.8 River River River Plume, Blind Bay Plume TABLE 2-Continued Minor phytoplankton species of the eastern Mississippi Delta Speciea Seaeon1 Are•• lound, CI . %., N. pacifica Cupp May1957 Plume N. palea (Kutzing) W. Smith May'l957 Plum e N. paradoxa (Gmelin) Grunow February 1956-1957 Plume Surirella sp. Turpin Fehruary, 1957 May Plume, Gulf S. fastuosa var. recedens May 1957 Plum e Other phytoplankton Chroococcus sp. Nageli Fehruary 1956 River, 0-0.8 Lyngbyesp. October 1955 Gulf N ostoc s p. Vaucher October 1955, February 1956-57 River, Plume Cylindroscapsa sp. Reinsch October 1955 Gulf Tetrastrum sp. Chodat Octoher 1955 River Actinastrum hantzschii Lagerheim . February '1956 River Ceratium sp. 'Schrank C. /urca (Ehrenberg) Claparede a·nd Lachmann C. tripos (0. F. Muller) Nitzsch C. /usus (Ehrenberg) Dujardin June, October, '1955 Gulf, Breton' Sound Glenodinium sp. Kelhs October 1955, May Gulf Goniodoma sp. Stein June, October Widespread in Gulf, nowhere abundant Pyrocystis Murray Junc;, October Widespread in Gulf, nowhere abundant P. pseudonoctoluca (W. Thompson) June, October Widespread in Gulf, nowhere abundant Hypodinium sphericum Kelbs J une, October Widespread in Gulf, nowhere abundant Gymnodinium sp. Stein J une, October Widespread in Gulf, nowhere abundant Gloeáinium s¡>. Kelbs June, October Widespread in Gulf, nowhere abundant Peridinium sp. Ehrenberg June, October Widespread in Gulf, nowhere abundant Hemidinium sp. Stein June, Octoher Widespread in Gulf, nowhere abundant Dinophysis sp. Ehrenberg ]une, October Widespread in Gulf, nowhere abundant D. caudata Saville-Kent June, October Widespread in Gulf, nowhere abundant Euglenopsis vivax Kelbs February 1957 River (from marshes) Phytoplankwn of the Eastern Mississippi Delta Kutzing was present in samples taken in September at Blind Bay and in February, 1957, in the plume. However, the heaviest population discovered, containing 1,490 cells/rnl, was taken in the plume near Pass-a-Loutre in May, 1957. This genus was often found together with C. meneghingiana and idtentification was usually difficult. Coscinodiscus excentricus Ehrenberg was abundant in September, 1956, in Breton Sound. The chlorinity was 18.37 %o and the water temperature was 25.8°C. C. nitidus Gregory was most abundant in the Gulf in November, 1956. Chaetoceros. The genus Chaetoceros was widespread in the delta and 26 species were identified. Only two oceanic forms are included in this group, the remainder being neritic. None were found at chlorinities less than 7.00 9"oo and, in general, the cnocen­trations were maximum in May, 1957, and June, 1955. There were also sizable popu~ lations in October, 1955, in the Gulf. C. lorenzianus Grunow, a tropical and temperate species (Cupp, 1943), was found in February, 1956 and in May, 1957, at severa! Gulf stations. One small concentration was encountered in October, 1955, in the Gulf. C. compressus Lauder was found only in the June, 1955, samples near Breton Island. The chlorinity was 12.35-15.24 %o and the water temperature was 23.6°C. Conover ( 1956) reported this species for all seasons in Long Island Sound with a spring flower­ing in May, 1953, and a peak in August, 1952. Her data indicate that low light in­tensity and high nutrient concentrations were necessary for this form. These condi­tions were met in May in the delta. Cupp and Allen ( 1938) list this as a very im­portant species in the Gulf of California in March, June, November and December. C. affinis Lauder was one of the most abundant representatives of the genus in February, 1956, May, 1957, and ]une, 1955. It was found in the Gulf at chlorinities of 14.0­ 17.0 %0 • Conover ( 1956) observed this species more often at offshore stations than at inshore stations in Long Island Sound but found the higher concentrations in August and September. Cupp ( 1943) lists this species as numerous from May through August off California. In the Mississippi Delta its peak of abundance coincides with the flood period. C. pelagicus Cleve was another species found in May, 1957, at offshore stations. Water temperature was 22.0ºC and chlorinity was 14.00-17.00 %0 • Conover's (1956) ex· perimental data suggest that it grows well in moderate light conditions if inorganic nutrients are present. C. diversus Cleve is a tropical and sub tropical species that was found in the Gulf in ali seasons but was most abundant in May. The concentration dropped sharply in June and there was a minor peak in October. Eunotia Ehrenberg was probably washed in from fresh water, since most species of this genera are calciphobic (personal communication from Dr. R. Patrick) and since it was found only in February, 1957, and May, 1957, during floodstage. Thalassionema nitzschioides Grunow, a north temperate species, was abundant in the delta. There were two widely separated peaks of abundance with the major one in October, 1955, anda minor one in May, 1957. At stations where the concentration was high, chlorinity ranged from 13.25 to 17.14 %0• These peaks are different from those reported by Cupp and Allen (1938). Thalassiothrix frauenfeldii Grunow was found everywhere in May, 1957, except in the river and in Blind Bay constituting an important part of the diatom flora. It was found at only two stations in September, 1956, and October, 1955, and isolated patches also were found in November, 1956, February', 1956, and February, 1957. This species was reported to be abundant in August, 1926, off southern California by Allen (1938). Sampling was not sufficient to tell if a double peak actually existed or if the dense isolated populations found in September and October were usual. Asterionella japonú:a Cleve, a widespread neritic species, in May, 1957, was present at all Gulf stations and was most abundant at a chlorinity range of 10.00---17.00 %o­In February, 1956, over 3,000 cells/ml were present in a bloom in Breton Sound, but it was not noted in other areas. The species was less abundant in October, 1955, anda few were found in November. In the delta this is apparently a late spring form with an elongated major peak from February to June in Gulf waters. There is ap­parently a shorter period of flowering in late fall. A. formosa Cleve and A. gracíllíma (Hantzschel) Beiberg, although never very nu­merous, were often found in the river and in areas of fresh water near the Gulf. They were most abundant during periods when the river was not at flood stage. Achnanthes. At least four species of the genus Achnanthes Bory were present in the delta (A. longpípes, A. mícrocepluila, A. depressus and A. speciosa). Because of the difficulty of obtaining accurate identification these are summarized together. The greatest concentration found was in Blind Bay and the plume in February, 1957. The genus was more widespread in May', 1957, than in February but cell numbers were less. Scattered patches were found in September, 1956, and November, 1956. Navícula. At least a few cells of the genus Navícula were found in almost every sample taken in the eastern Mississippi Delta. N. rhyncocephala Kutzing was found only in the primary plume or in fresh water. N. gracílís Ehrenberg was similarly distrib­uted except that it was taken in chlorinites as high as 6.00 %0 • N. dístans (W. Smith) Ralfs was found in fresh water in May, 1957, and was present at nearshore stations throughout the year, being most abundant at chlorinities of 5.00-12.00 %o· Gyrosígma. Species of the genus Gyrosígma Hassall were found in every season except June, 1955. However, the only times it assumed a position of importance were in October, 1955, in Blind Bay, and in February, 1957, in Breton Sound. In the latter case, C. baltícum was the species present. Nitzschia. Sorne species of the genus Nitzschía Hassall were present in every season except November, 1956. The most dense populations identified only to genus were found in the Gulf off Pass-a-Loutre in )une, 1955, and in February, 1957. N. bílo­bata var mínor Grunow was present at chlorinities ranging from 1.92 to 17.14 %0 • N. closteríum (Ehrenberg) W. Smith was taken in October, 1955; February, 1956; and May, 1957, and was widespread in October and May. Highest cell concentrations were found in areas of moderate chlorinity ( 4.00-12.00 %o) and at stations near the plume or river. N. longissima (Brebisson) Ralfs was found in February, May, September and October, but was abundant only in the Gulf in February, 1957. The chlorinity tolerance was great (1.00---18.00 %o) but highest cell numbers were found near the plume. Conover (1956) found that high temperature, moderate to high light intensity and enriched water seemed favorable for growth of this species. Most of these conditions are met just outside the plume. N. seriata Cleve was widespread in the area and was most numerous in May, 1957, June, 1955, and in October. Smaller numbers were found in February, 1956, and 1957 and none were taken in September or November. This species was most abun­dant at chlorinities above 13.00 %o and at temperatures of 20.0-23.0ºC. Discussion PHYTOJ>LANK'fON PoPULATIONs DuRINGtACH FIELD TRIP IN RELATION TO ffYDROGRAPHICAL AND METEOROLOG1CAL CONDITIONS The five general areas varied considerably from each other and there · w~re pro­nounced seasonal differenc~s in phytoplankton populations. These are shown in Table 3 together with other data on nutrients and physical factors. In June, 1955, the river was turbid although the peak of the flood season was past. In the river and the barely detectable plume most diatoms were of the genera Melosira and Cyclotella. In the Gulf and in Breton Sound Skeletonema costatum and Cheatoceros spp. were abundant. In October, 1955, the river was low and clear. Phytoplankton was sparse in this area and composed of the Melosira·Cyclotella complex. In the Gulf and at Breton Island u'iost of the genera were marine but populations were extremely variable from station to station ancl on successive days. Thalassionema nitzschioides and Skeletonema costatum were abundant at most stations. In February, 19S6, with the river at flood stage, swift and turbid, the primary plume extended far into the Gulf. Cell numbers were high throughout the river and the Melo­sira-Cyclotella c~mplex was very evident. Near Breton Island a "pulse" of diatoms occuried with Skeletonema costatum as the major species. During September, 1956, the river was low and clear and the plume was not pro­nounced. Chlorinity was fairly high, even in the river. V arious species of Coscinodiscus were abundant in Breton Sound, species of Mel~sira and Cyclotella were common in the river and Blind Bay, and samples from the plume area varied, on successive days, from purely marine to fresh water forms. A "pulse" of Cyclotella caspia was present near Breton Island on September 10 with cell concentrations of 4,300/ml recorded. In November, 1956, the river was again very low and very clear. Phytoplankton was nowhere abundant and this was apparently the season when populations were least dense in the eastern delta. The most abundant species was Asterionella formosa. Samples taken in February, 1957, were from the river, which was again at flood stage, and from the plume which was very pronounced. Results were similar to those obtained in February, 1956. During the period from May 1 to May 7 the river was still at flood stage and was very turbid. However, seasonal high tides flowing inward forced the plume into a narrow band near shore. Water temperatures had risen sharply since the winter sampling, and there was a distinct border between Water from the river and from the Gulf as•evidenced by phytoplankton populations and by hydrographic factors. Data from traverses across the plume into the Gulf are given in Tables 4 and 5. In the river and in the plume most plankton were of the Melosira-Cyclotella complex, and 10 species were identified. In the Gulf there was extreme diversity and patchiness of phytoplankton with over 30 species found at sorne stations. Dominant genera were Chaetoceros, Thalassionema, Asterionell.a, and Skeletonema. Cell concentrations were high for marine species in comparison to TABLE 3 Seasonal conditions in the eastern Mississippi Delta with regard to phytoplankton abundance and hydrographic factors Season Are a Primary phytoplankton Total cells/ml CI. %c Water temp . QC PO.-P ug al/I Si03-Si ug at/l Suspended solide rng/I Remarks June 1955 M elosira spp. Cyclotella spp. 1000 0.06 22.5 1.70 161.0 River at flood stage 2 Cyclotella sp. Skeletonema costatum Chaetoceros alfinis 1300 15.71 23.7 3.00 3 Cyclotella spp. 1300 16.01 ZS.8 2.40 24.0 4 Skeletonema costatum Chaetoceros alfinis 2800­3500 12.35­15.24 23.6 53.0 October 1955 Cyclotella spp. M elosira spp. 100 1.61­2.iJ:l 28.0­28.6 64.0­68.0 12.0­14.0 River clear, low 2 Scenedesmus spp. Cyclotella spp. Melosira spp. Skeletonema costatum 500 6.03­7.06 28.9 47.0­61.0 34.0 3 T halassionema nitzschioides Nitzschia closterium T halassiothrix fraunenfeldii 400­2000 15.83­17.14 28.4­28.8 9.6­13.0 34.0­38.0 4 T halassionema nitzschioides 274­2300 13.25­14.33 27.0­27.4 .28.0­36.0 30.0­40.0 5 Cyclotella sp. Gyrosigma sp. 2300 5300 3.56­4.10 40.0­79.0 February 1956 1 M elosira granulata Coscinodiscus spp. 3400 .04±.01 8.5±.5 75.5 Riververy muddy, swift 2 Melosira spp. Cyclotella spp. Skeletonema costatum 1200 1.71 16.5 2.40 64.2 TABLE 3-Continued Seasonal conditions in the eastern Mississippi Delta with regard to phytoplankton abundance and hydrographic factors Season Are a Primary phyloplanklon Tolal cells/ ml Cl.%,, Water temp. ºC PO,-P ug al/I SiOa·Si ug al/I Suspend<'d solíJs mg/ I Remarks 4 Skeletonema costatum Coscinodiscus spp. Rhizosolenis stolterforthii Chaetoceros spp. Asterionella japonica Nitzschia spp. 20,000 '15.91 15.9 5 M elosira spp. Cyclotella sp. 2500 0.04 13.0 Septemher 195ó Cyclotella comta M elosira spp. 1000 3.50 27.l 3.76 Clear, low river discharge 2 M elosira distans Coscinodiscus spp. 100­270 6.01­1'3.50 27 .5­28.1 3.56-­4.09 4 Cyclotella caspia Coscinodiscus spp. Thalassionema nitzschioides 838-4300 15.1­18.4 25.8­26.0 2.81­2.91 November 1956 Asterionella formosa 53 3.3'1 24.0 0.96 25.5 Low river, clear water. Secchi reading 72 inches 2 A . formosa 0-113 13.26 22.0 1.00 18.4 20.0 Secchi= 48-244 inches 3 A. japonica M elosira su/cata 19.71 23.6 58.4 4 1 15.5 18.0 TABL E 3-Continuecl Seasonal eonclitions in the eastern Mississippi Delta with regarcl to phytoplankton abunclanee ancl hyclrographie faetors Season Area Primary phytoplankton Total cells/ml Cl. %o Water temp. ºC P04-P ug al/ ! Si03-Si ug al/I Suspended !'olidii mg/ l Remarks February 1957 1 Melosiraspp. M. granulata M. distans 2500 average O.O­0.04 10.0-­14.0 0.73­1.77 60.0­100.0 500.0-­600.0 River turbicl, swift ancl flooclecl. Seeehi clise= 2 Cyclotella s¡1p. C. comta C. meneghiniana Cyclotella sp. Melosira spp. Plagiogramma vanheurkii Thalassionema nitzschioides 574­4500 0.07­14.0 13.2­16.0 3-6 inehes Seeehi clise= 6-24inehes 5 M elosira sp. Cyclotella sp. 6000 0.04 13.4 500-­600 May 1957 Melosirasp. Cyclotella sp. 2700 0.07 19.5 0.36 River high ancl turbicl. Seechi clise=l ineh 2 Cyclotella meneghiniana M elosira distans Asterionella japonica Chaetoceros spp. 304-3800 0.58­6.54 19.4­2'2.5 31.0-­168.0 Seeehi clise= 36-144inehes 3 Chaetoceros sp. e. vanheurkii C. affinis 23S.-:1000 8.64­17.93 22.3 23.9 16.0-­23.0 Seeehi cl ise= 36-1'44 inehes Thalassionema nitzschioides Asterionella japonica N itzschia sp. Skeletonema costatum Eunotia spp. Phytoplankton of the Eastern Mississippi Delta TABLE 4 Diatom cell concentration and hydrographic conditions on a traverse from the plume to the · Gulf in May, 1957 Water Seccbi Su1pended _ Concentration Cblorinity lemperature disc 101id1 of cella No. of Station •e mg/I number/ml 1pede1 %c 985 08.64 212.2 1 23 605 19 986 '14.08 24.5 2.5 14 441 '10 987 15.11 23.9 4 20 866 '20 TABLE 5 Closely spaced stations on a traverse in the Gulf in May, 1957 Water Seccbi Suspended Concentralion Station Chlorinity %c temperature ºC disc solids mg/I of cella number/ml No. of specie1 990 13.69 23.0 1.5 21 463 20 992 15.69 22.7 '2.0 19 662 '26 993 16.29 22.7 '2.2 23 998 26 994 17.'20 22.7 2.5 16 233 26 995 17.7 22.2 3.5 --­ 411'1 19 996 17.90 22.7 3.7 20.0 7Sl. 46 ·996B, 17.93 22.7 20.0 3'12 29 subsudace those at other seasons, but concentrations were still less than those in the river and plume. GENERAL REMARKS ON THE TEMPORAL AND HORIZONTAL DISTRIBUTION OF DELTA PHYTOPLANKTON In order to summarize these data, a table has been prepared showing the horizontal distribution of the primary phytoplankton genera during each field trip (Tahle 6). A genus is listed as major if it formed more than 50 per cent of the population from any one sample in each area. The genus is also listed as major if it comprised more than 5 per cent of the population in the majority of stations in each area. From Table 6, it is apparent that the river (Area 1) is the most uniform area throughout the year, with Melosira and Cyclotella the major genera at most times. At flood stage, the river always had a high cell concentration. These cells may have been transported many miles, since the cell concentration during February, 1957, was nearly homogenous throughout the river and the cells, although in poor condition, were still living. Phytoplankton concentrations were lowest in the fall when the stream flow was at a minimum. These facts appear to be contrary to sorne of those reported by Kofoid ( 1903), Cil­leuls (1926), and Pearsall (1923), as summarized by Blum (1956). These investí· gators reported a sharp decline in phytoplankton during periods of higher water. The decline was followed by an immediate "pulse" or "bloom." Kofoid, however, felt that stable water conditions might enhance phytoplankton production. In terms of the usual hydrographic measurements ( chlorinity, water temperature, turbidity and current flow), the Mississippi is certainly most stable during times of high water. Transeau TABLE b Horizontal distribution of primary phytoplankton genera in the eastern Mississippi Delta . . Cell number per millilite+ given in 'parentheses Area 1 Area 2 . Area 3 Area 4 Area 5 River Plume Gulf Brelon SoUJ1d Blind Bay June, 1955 Melosira (1109) Skeletonema (2575) Cyclotella (695) Skeletonema (30'22) Clyclotella Cyclotella Chaetoceros · Chaetoc'eros October, 1955 M'elosira ·. Melosira (540) .Cyclotella (1293) T halassionema (ISIO) Cyclotella (4306) Clyclotella Cyclotella Thalassionema · Nitzschia Coscinodiscus .T halassiothrix Chilomonas Skeletonema NiiZschia Scenedesmus Chaetoceros February, 1956 Melosira (3341) Melosira (1216) Skeletonema (22097) Melosira (2461) Coscinodiscus Chaetoceros Cyclotella Asterionella September, 1956 Cyclotella {1031) Melosira ('244) T halassionema ( 2536) M elosira ('291) Synedra Coscinodiscus Cyclotella Achnanthes Achnanthes Cyclotella November, 1956 Asterionella (53) M elosira (40) Melosira (58) Chaetoceros (l) Asterionella Cyclotella Skeletonema T halassionema Chaetoceros Navicula February, 1957 Melosira (2665) Melosira (2202) Melosira (5171) Clyclotella Nitzschia Cyclotella Asterionella Thalassionema May, 1957 Melosira (2667) · Melosira (653) Chaetoceros (757) · Clyclotella Asterionella Skeletonema Chaetoceros Asterionella Cyclo,tella Eunotia Cyclotella (1916) stated that algae in fresh waters seemed to be most numerous at time of high water. This was true of diatoms in the Mississippi. Melosira was absent from river samples taken in November, 1956. Cyclotella was still present, but the primary genus was Asterionella. Both fresh water and marine species of the latter genus were found. The disappearance of M elosira and the promi­nence of Asterionella was probably due to an increase in chlorinity from· approximately 0.05 %o during high water to 3.07 %o during November, 1956. It is possible that this salt intrusion limited phytoplankton growth. The probable limiting factor during flood stage was turbidity of the water. In Blind Bay (Area 5), the primary phytoplankton genera were the same as those in the nearby river. During flood stage a strong current of river water flowed into this hay. This area was not sampled in late spring or summer. At that time strong flushing action of spring tides could have introduced marine species into thi~ hay and also increased the water temperature greatly. In contrast to the relatively simple populations in the river and in Blind Bay, the populations in the plume (Area 2) were more complex. There was an increase in the number of major genera (see Table 6) due to an admixture of marine genera. From station to station within the plume, various dominant genera made up highly differing proportions of the total population. There were also great differences in the total cell concentration from station to station. At any one location in the plume cell concentra­tion changed greatly from day to day. There were two instances where the conditions in the plume paralleled those in the river. In November, 1956, the cell count was much lower than during other seasons. This low concentration was found in the river and generally throughout the Delta waters. Another instance of parallel behavior occurred in February, 1956, when a wide­spread plume of fresh, cold, muddy river water extended in a thin lay·er over the Gulf water. Such a plume has been traced far out to sea by Scruton and Moore (1953). This water was populated chiefly by M elosira which was also the major genus in the rivn. The Gulf seaward of the plume (Area 3) was not sampled often enough to give a complete annual picture of the distribution of the phytoplankton. Bad weather hampered operations during the two winter field trips, and with the exception of the May, 1957, trip, only a few stations were occupied. The populations in this area were complex in the same manner as in the plume, with more major genera than in the river dueto mix­ture of marine and fresh water genera, rapid changes in the population at any one lo­cation, and great differences from station to station. This complexity is illustrated by the description of conditions prevailing during the May, 1957, field trip, when the offshore area was sampled extensively. The total cell concentration varied from 16 to 3,781 cells/ ml at 19 stations sampled. Among these stations, the ranges in per cent of total sample, for major genera were as follows: Chaetoceros, 0-61% ; Skeletonema, 0--23 % ; Asterionella, 0-47% ; Thalassionema, 0-45%; Eunotia, 0--58% ; ThalassW­thrix, 0--35% ; Melosira, 0-28% ; Cyclotella, 0--86%; and Nitzschia, 0--34%. Thus, at any one station a major genus was sometimes absent, but was dominant at another stiation within the offshore area. It is apparent from Table 6 that the minimum total population in Area 3 was found in November, 1956, and in this respect this offshore area paralleled the other areas. Breton Sound (Area 4) occupies an intermediate position between the river and the offshore areas in tenns of the complexity' of its hydrography and phytoplankton popu­lations. Because of its sheltered position away from the main mouths of the river and behind Breton Island, it is probably less affected by currents and tides than the rest of the areas. This is indicated by current maps published by Scruton (1956) and by the fact that even during flood stages, the plume does not extend into Breton Sound. The population in Breton Sound fluctuates from nearly none to a strong "bloom." A suc­cession of major genera occurs in the Sound. Skeletonema was prominent from February to June, and was succeeded by a mixture of other genera later in the year, particularly by Thalassionema and Chaetoceros. Counts of phytoplankton showed that during any one season, the concentrations did not differ from area to area. In the fall months, the concentration in the river was significantly' less than at times of high river discharge (February or May). This was also true for the plume. In the Gulf, however, no significant seasonal differences were found. Certain primary phytoplankton species were significantly associated with each other. Fager's (1957) method of testing for significant (p = O.OS) associations was used (Table 7). Two such associations were recognized by this test. One, the river population, consisted of Cyclotella comta, C. meneghiniana, Melosira distans, M. granulata, Navi­cula gracuis, and N. rhyncocephala. The other association, the Gulf population, con- TABLE 7 Association of primary phytoplankton species with each other -= no significant association, += significant association @ .05 confidence level .¡ t :§ il E ~ il ••s • ·~ • !! • :.!! o • 8. •• 1 § .. § .!!_ E -~ -~ ""¡¡. ·~ .~ ~ -~ .~ !! 8 :¡;• .,, ... •E 1 ;¡ a 3 3 8 . • ~ .~ "" ::' ~ 3 :¿ .• ... -~ '! • • a ~ -~ ~ • . .~ s ¡¡ ~ ·¡¡ -:: "i ~ :¡; o Species a ] ... • ~ ::;i • ¡.., ... .;: ¡.., '-' G ! i ""'-' G G "" "' "' "' Cyclotella comta o + + C. meneghiniana o + + + Melosira distans o + + + + M. granulata o + + Navícula gracüis o + + N. rhyncocephala o + Nitzschia seriata o + + + + Thalassionema nitzschioides -+ o + + + + + Skeletonema costatum o + + + + Asterionella japonica + + + o + + + Chaetoceros affinis o + + + + + + C. decipiens o + + + C. diversus o + + + Thalassiothrix frauenfeldii o + + + sisted of Nitzschia seriata, Thalassiothrix frauenfeldii, Thalassionema nitzschioides, Skelewnema costatum, Asterionella japonica, Chaetoceros affinis, c. decipiens, and C. diversus. Severa! other species were not significantly associated with any other. The members of on~ association were not associated with members of the other association. The river association was found in the river and plume, and only rarely in the Gulf. Conversely, the Gulf association was found in the Gulf and plume, and only occasionally Phytoplankton o/ the Eastern Mississippi Delta in the river. The plume was thus an area where hoth associations were found. Blind Bay generally contained the river association, while Breton Sound geherally contained the Gulf association. The river association was found in waters of 0-10 %o chlorinity, but generally not in more saline water; the reverse was the case with the Gulf association. In our previous paper (Thomas and Simmons, 1960) we noted that at a plume sta­tion, occupied on three successive days, phytoplankton production increased seven-fold the second day and then decreased on the third day to approximately the original levd. The phytoplankton concentration also decreased on this third day and this was ac­companied by an increase in chlorinity. On the second day the major phytoplankt<>n species at this station was Melosira distans, while more typically marine species were found as well on the third day. It is possible that this decrease in production was the result of the change in chlorinity which may have damaged cells of the freshwater species, Melosira. The fact that the river association is carried into the sea and is found at plume stations, but only rarely at Gulf stations, suggests that these freshwater species are destroyed by the increased chlorinity. The fate of these species is worthy of further investigation. Sediments taken just off the mouth of Pass-a-Loutre were examined and contained many cells of these freshwater species. COMPARISON WITH ÜTHER AREAS King (1949) examined samples taken off the west coast of Florida and found that conditions there were similar in many respects to those in the Mississippi Delta. The actual volume of plankton was very fow compared to northern waters but the variety was much greater. The Delta, in spring, is apparently even more diverse, since over 30 genera of diatoms were obtained from a 60 ml unconcentrated sample as compared to 11 genera obtained from 1600 liters of water in Florida. Packed cell volumes of un­concentrated water samples were obtained in the Florida waters. One nearshore sample there contained 0.0806 ml of solids per liter of water. This was exceptionally high for that area, the next highest value listed being 0.0359 mi. Samples collected near the 10 fathom line gave values ranging from 0.0012-0.0271 ml per liter of water. The figure given for May from this location was 0.0043. As a comparison, the calculated value at the 10 fathom line for May, in the Delta, was about 0.0050 mi. Ali of these figures in­clude sediment and the Florida figures include zooplankton as well. May, of.course, was the month when phytoplankton appeared to be most abundant in the Delta along this depth line, whereas August was more productive in Florida water. However, from an examin'ation of ali of the values given for Florida statións in King's survey it would ap· pear that the two a reas are quite similar, i.e.,. there is a peak in May or June with an­other peak occurring in late summer or fall, and a decline later in the year. The actual number of phytoplankton cells in Florida is somewhat less than in Delta waters, a a difference possibly explainable in that a Ciark-Bumpus net was used in Florida while unconcentrated water samples were used in the Delta. Curl (1959) listed 90 species of diatoms from the northeastern Gulf of Mexico, pri­ marily from Apalachee Bay and Alligator Harbor. In many ways the phytoplankton of that area resembled that of the eastem Mississippi Delta. Notably absent from Flo.rida waters was the genus Cyclotella and severa! ~pecies of Melosira. Species common in the Delta and absent or uncommon in the northeastern Gulf include Coscinodiscus nitidus, Chaetoceros compressus, C. costaJ,us, C. pelagicus, C. brevis, Diatf!ma spp., Eunotia spp., Plagi.ogramma vanheurkii, Achnanthes spp. and Navicula spp. Forms found to be ahundant in the northeastern Gulf but ahsent or rare in the Delta include Eupodiscus radiatus, Certatulina pe/,agica, Triceratium favus, Eucampia cornuta, Rhizosolenia afuta, and R. stolterforthi. Biddulphia aurita, Clwetoceros gracüe, Achnanthes spp., and Cocconeis spp., listed by Curl as rare in the Gulf or not previously reported, were fairly common in the eastern Mississippi Delta. Chaetoceros dichaeta given by Curl as a first record from the Gulf was not found in the Delta. Many forms were probably found in the Delta but not in Florida because of the proximity of a large river~ There were extreme patchiness and irregular distribution of species in both areas but in the Delta most phy­toplankton was found near the surface whereas in the Florida waters there were no sig­nificant differences between depth samples. Freese (1952) found more than 70 species of diatoms in the area of Rockport, Texas, although the blooms reported in his paper occurred severa] months before the general peak in the Delta. However, the heavy bloom reported in February near Breton lsland corresponds well to sorne found in equally protected Texas hay areas. In Texas sorne oceanic species such as Thalassiothrix frauenfeúlii and Rhizosolenia alata appeared first in the spring at Gulf stations and the progressed further inshore (Freese, 1952). This might indicate that, in the Delta, the May peak is caused by a similar inward progres­sion of diatoms in May or June. Many forms, of major importance in Texas bays, were not abundant off the Mississippi Delta. The presence of several cold water species in Texas waters, notably Skeletonema costatum, was attributed to heavy runoff from the Guadalupe River and this form was also very abundant in the Delta near the water source. However, this species was found by Simmons to be abundant in Septernber, 1956, in the Texas Laguna Madre, a hypersaline hay. Simmons (1959) also found that tychopelagic diatoms were abundant in the hyper­saline Laguna Madre and that blooms occurred in September after tidal flats were flooded by high tides. Many species found in the Gulf areas of the eastern Delta were also present in the Laguna Madre but the major phytoplankton in the latter case were blue-green algae. Bigelow (1926) found an entirely different seasonal trend in the Gulf of Maine with the lowest numbers occurring in late February and early March and the highest peak, as a rule, in April. The composition of the plankton varied greatly from that of the Mississippi, and the counts were much higher. In sorne respects the diatom flora in the Delta resernbled that found off southern Cali­forrnia. Allen (1936) found that such forms as Chaetoceros sp. were most abundant in the spring and that filiform genera, such as Thalassionema sp. were more abundant in the fall . Perhaps the chief difference between the areas is the larger number of littoral and tychopelagic forms found in and near the river and swamps. Srnayda (1957) found that most of 75 species recorded in lower Narragansett Bay were diatoms, but in sorne instances dinoflagellates were present in greater concen· trations. The peaks found there for Skeletonema costatum_ and Asterionella japonica were reversed seasonally from those found in the eastern Mississippi Delta. Conover (1956) reported that in Long lsland So\lnd diatoms were prominent except during the summer when these were l¡µgely replaced by dinoflagellates and flagellates. She reported a clear-cut succession of species and changes in abundance from year to year. A variation in abundance was noted in the eastern delta, but there was no clear­cut succession except in isolated areas. Summary l. Phytoplankton collections were made from 134 stations in the eastem Mississippi Delta region. The entire region was divided into five general areas representing differ­ent habitats. Seasonal variations in phytoplankton composition and quantity were an­alyzed, and an attempt was made to correiate these variations with various ecological factors. A partially annotated checklist was prepared with notes in the phytoplankton species found during the survey. 2. Over 200 species of phytoplankton, most of which were diatoms, were noted during this survey. Two associations of phytoplankton species were recognized. One, the river association, consisted of species of Cyclotella, Melos ira, and N avicula. The other, the Gulf association, was made up of species of Nitzschia., Thalassionema, Thalasswthrix, Skeletonema, Asterwnella, and Chaetoceros. Both associations were found in a zone of mixing of fresh water with sea water, designated the primary plume. 3. During the February trips, river discharge was very great and the plume extended far out into the Gulf. The river population was found at ali plurne and river stations and in Blind Bay. However, samples taken in more saline water underlying the plurne and in Breton Sound contained a typical marine population. Cell numbers were rela­tively higher than in the fall months. 4. In May and June, conditions were similar to those of February. However, water temperatures were higher and the plume did not extend as far to sea, being modified by incoming high tides of the spring of the year. 5. In September, sorne marine forrns were present in the river along with the usual river population. Chlorinities were also greater at the river station. The plume station showed variable populations and chlorinities. Cell concentrations continued to be rela­tively greater than those of the fall months. 6. Samples taken during October and November contained less phytoplankton than those taken at any other season. Although chlorinities approached 3.0 %o in the river, the usual river population was found. The river was low and rnuch clearer than at other seasons. A rnixed river and Gulf population was found at plurne stations, and a Gulf population was present at Breton Sound and in the Gulf. 7. In comparison with other parts of the seas, the eastern Mississippi Delta has a low concentration of phytoplankton, but in cornparison with other nearshore areas in the Gulf of Mexico, both the cell concentration and the numher of species are large. Acknowledgments Boats for rnost of the field trips were furnished by the Louisiana Wildlife and Fish­eries Commission. Gratitude is expressed to all personnel of the Cornmission for helping to make this survey possible. Mrs. Frieda M. N. Reid made sorne of the slide counts in the earlier field trips and Robert Holrnes has aided in identifying phytoplankton and has critically read the manuscript. The entire program was sponsored by the Amer­ican Petroleum lnstitute which supplied funds for research and salaries. Literature Cited Allen, W. E. 1936. Occurrence of marine plankton diatoms in a ten-year series of daily catches in California. Amer. J. Bot. '23: 60-63. ----. '1938. The Templeton Crocker expedition to the Gulf of California in 1935-the phytoplankton. Trans. Amer. micrn. Soc. 57: 3'28-3'35. Bigelowl H. B. 19'26. Plankton of the offshore waters of the Gulf of Maine. Bull. U. S. Bur. Fish. 40(2): 1-509. Blum, John L. 1956. The ecology of river algae. Bot. Rev. 212 (5) : 291-3411. Bien, G. S., D. E. Cont()is, and W. H. Thomas. 1958. The removal of soluble silica from fresh water entering the seas. Geochim. et comsoch. Acta 14: '35-54. Cilleuls, J. des. 1926. Le phytoplancton de la S()ire. Compt. Rend. Acad. Sci. (Paris) 182: 649-651. Conover, 'Shirley. 1956. Oceanop:raphy of Long Island Sound. 1952-1954. IV Phytoplankton. Bull. Bingham oceanogr. Col!. 15: 62-112. Cupp, Easter E. 1943. Marine plankton diatoms of the west coast of North America. Bull. Scripps lnstn Oceanogr. 5('1) : 1-238. Cupp, E. E., and W. E. Allen. 1938. Plankton diatoms of the Gulf ()f California obtained by Allan Hancock Pacific expedition of 1937. Univ. South. Calif. Press, Allan Hancock Pacific Exped. 3: 61-99, pls. 4-15. Curl, Herbert C, Jr. 1956. The hydrography and phytoplankton ecology of the inshore, northeastern Gulf of Mexico. Doctoral Dissertation, Florida State University. ----.. 1959. The phytoplankton of Apalachee Bay and the northeastern Gulf ()f Mexico. Pub!. lnst. Mar. Sci. Univ. Tex. 6: 277-3'20. Dienert, F., and F. Wandenbulke. 1923. Sur le dosage de la silice dans les eaus. Compl. Rend. 176: 1478-1480. Fager, E. W. 1957. Determination and an·alysis of recurrent groups. Ecology 38: 58fr'595. Freese, Leonard R. 1952. Marine diat()mS of the Rockport, Texas hay area. Tex. J. Sci. 4(3): 331-386. Holmes, R. W., and Freda M. H. Reid. (In press). The preparation of marine phytoplankton for microscopic examination and enumeration on molecular filters. Hustedt, F. 1930 et seq. Die Kieselalgen. In Rabenhorst's Kryptogamen-Flora, Vol. 7, 11 Teil, 2 Teil. Akad. Verlagsges. m. h. H., Leipzig. King, J. E. 1950. Plankton ()f the west coast of Florida. Quart. Jour. Fla_ Acad. Sci. 12 (2) : 109-137. Kofoid, C. A. '1903. The plankton of the Illinois River, 1894-1899, with introductory notes upon the hydrograp·hy of the Illinois River and its basin. Part l. Quantifative investigations and general results. Bull. Ill. State Lab. Nat. Hist. 6: 95-6'29. McHargue, J. S., and A. M. Peters. 19'Zl. Removal of min'eral plant food by natural drainage waters. Kentucky Agr. Exp. Stat. Bull. No. 237. Parker, R. H. 1956. Macro-invertebrate assemblages as indicators of sedimentary environments in east Mississippi Delta region. Bull. Amer. Assoc. Petrol. Geol. 40(2): 295-376. Pearsall, W. H.192·3. A theory of diatom periodicity. J. Ecol. 11: 165-183. Riley, G. A. '1937. The significance of the Mississippi River drainage for biological conditi()ns in the n()rthern Gulf of Mexico. J. Mar. Res. ·1('l') : 60-74. Rochford, D. J. 1951. Studies in Australian estuarine hydrology. I. lntroductory and comparative features. Aust. J. Mar. Freshw. Res. 2(1): 1-116. Schiller, J. 1933 et seq. Dinoflagellatae. In Rabenhorst's Kryptogamen-Flora, Vol. 10, Abt. 3, 1 Teil, 2 Teil. Akad Verlagsges. m. h. H., Leipzig. Scruton, P. C. 1956. Oceanography of Mississippi Delta sedimentary environments. Bull. Amer. Assoc. Petrol. Ge()!. 40(1'2) : 2684_.:2952. Scruton, P. C., and D. G. Moore. 1953. Distribution of surface turbidity off Mississippi Delta. Bull. Amer. Soc. Petrol. Geol. 37: lü67-74. Shaw, E. W. 1913. The mud lumps at the mouth of the Mississippi. U. S. Geol. Survey. Prof. Paper 85B: 1111...:27. Shepard, Francis P. 1954. Nomenclature based on sand-silt-clay ratios. J. sediment. Petrol. 24: 151-158. Simmons, E. G. 1957. An ecol()gical survey of the upper Laguna Madre. Publ. lnst. Mar. Sci. Univ. Tex. 4('2) : 156-200. ----. 1959. Qualitative and quantitative survey of phytoplankton in waters ranging from brackish to hypersaline. In Project Reports for 1958-59. Marine Fisheries Division, Texas Game and Fish Commission. Smayda, T. J. 1957. Phytoplankton in lower Narragansett Bay. Limnol. Oceanogr. 2(4): 342--359. Smith, G. M. 1933. The freshwater algae of the United States. McGraw-Hill, New York. Thomas, W. H. and E. G. Simmons. 1960. Phytoplankton production in the Mississippi delta, p. 103-116. In Recent 'Sediments, Northwestern Gulf of Mexico. Amer. Assoc. Petrol. Geol., Tulsa, Okla. Transeau, E. N. 1916. The periodicity of fresh water algae. Amer. J. Bot .3: '121-'13'3. Tulane University Zoology Dept. 1954. Biological study of Lake Pontchartrain. Progress report for period ending January 31, 1954. Wooster, W. S., and N. W. Rakestraw. 1951. The estimation of dissolved phosphate in sea water. J. Mar. Res. 10: 91-100. Fishes of the Río Tamesí and Related Coastal Lagoons in East-Central Mexico1 REZNEAT M. DARNELL Department of Biology, Marquette University Milwaukee, Wisconsin Contents Page } NTRO DU CTI O N ---------------------------------------------------------------------------------------------... _.. _.. _.... . . 300 HISTORY -------------------------------------------------------------·-··-··---·········--···-··-----·····-·-·-·-···--·------··· 302 GEOGRAPHY AND GEOLOGY --------------------------------------------------------------------......... -....-----. 304 PRECIPITATION ----------------------------------------·········· ·-·--··· ···· ··-···-----··--··-····-··-······-·--······ ··----304 DRAINAGE ---------------------------------------------------------------· -..... -..... -.... -.. -. -.... -. ----. -........ -----. ---. 306 CoLLECTING STATIONS IN THE Río TAMESÍ SYSTEM ················------······-····· ·-········-··--·· 309 ANNOTATED LIST OF SPECIES --------------------------------------------···········•···-···········----···········-319 ZooGEOGRAPHic DiscussION -------------------------------------------------------------. _............ ----·. 351 PROVISIONAL CLASSIFICATION OF Río T AMESÍ FISHES BASED ON APPARENT SALINITY TOLERANCE ------------------------------------------------·········· ·········-----354 SUMMARY ......_.. _. -------------------------------------------------------------· ...----.... _ ............ ............ _____.... 359 AcKNOWLEDGMENTS ································· ··········--·······---··············-·······-·········-······-······· 360 LITERATURE CITED ··-····--······-···-····-······-···-·········-······························· ······················-···· 361 Abstract A total of 11,043 specimens of fishes was obtained in 66 collections from the tributaries of the Río Tamesí and from a coastal lagoon near Tampico. 'Sixty species of fishes are now recognized from the area, 23 of which are fresh-water forms and 37 of which are considered to be euryhaline. For each species information is given, if available, regarding the following: nomenclature, distribution, salinity relations, general ecology, food habits, and reproduction. The 23 fresh-water species in elude strictly fresh-water forms (15), sporadic invaders of low salinity water (4), and frequent invaders of low salinity water (4). The 37 euryhaline species include anadromous forms (4), catadromous forms (2), frequent invaders of fresh-water (5), sporadic invaders of fresh-water ( 9), and marine species which are facultative invaders of low salinity water (17) . Twelve of the species are considered to be endemic in the Pánuco-Tamesí system, ali of which are strictly fresh-water forms. For both the fresh-water fishes 'and the littoral marine fishes, eastern Mexico represents a zone of transition between the temperate and tropical faunas. Among the fresh-water species of the Tamesí, representatives of southem families slightly outnumber representatives of northern families (13 :10). Among the euryhaline species, representatives of southern families greatly predominate over those of northern families (39:2). Analysis of habitat distribution of the fresh-water fishes of the Tamesí reveals that those of southern derivation inhabit primarily the small upstream waters, whereas those of northem affinity are chiefly inhabitants of larger and downstream waters. These phenomena are discussed in terms of fauna( centers and barriers to dispersa!. 1 Contribution No. 6 from the Laboratory of Hydrobiology, Department of Biology, Marquette University. Introduction In 1950 the writer initiated a series of studies on the ecology of aquatic communities in the headwaters of the Río Tamesí drainage in east-central Mexico. A portion of this material was incorporated into his doctoral dissertation presented to the faculty of the University of Minnesota (Darnell, 1953). Although the studies were primarily con­cerned with the composition and trophic structure of the subtropical aquatic communi­ties, problems of taxonomy in the various aquatic groups inhabiting this poorly known area have delayed the appearance of the general ecological treatise. This delay has been occasioned, in part also, by the hope that the manuscript of Hubbs and Gordon on the fishes of northeastern Mexico, imminent for over twenty years, would finally make its appearance. With the recent death of Dr. Gordon the present writer is hesitant to delay further the publication of his ecological work and so has prepared this paper as a back­ground for the ecological study already accomplished, but still unpublished. It was originally intended that the present article should include only the strictly fresh-water fishes of the Tamesí system. This was rendered impossible by the following circumstances. the lack of detailed habita! data for most of the species in the important coastal collections of Jordan and Dickerson (1908), the fact that the writer's Laguna de Chairel collections contained a number of typically brackish water or marine species, and also by the fact that many of the headwater species probably or definitely do not honor the bounds of strictly fresh water. Thus, in the absence of any sharp dividing line, it was decided to include the work of Jordan and Dickerson ( 1908) and to summarize the present status of our incomplete knowledge of these forms as a point of departure for future work. Sewral species. so far not recorded from the drainage, are expected to be found when the larger streams and the lagoons around Tampico are adequately sampled. None are included in the present work, however, unless specimens have been reported directly from the drainage (or from coastal a reas near the drainage in the case of Fundulus similis and certain forms included in Jordan and Dickerson's collections). This ex· eludes a number of fresh-water, brackish-water, and marine species whose known dis­tributional ranges extend on both sides of the Tamesí, as well as certain species pre­viously encountered in the Río Pánuco but for which specimens have not yet been taken from the Río Tamesí. Bailey. Winn and Smith (1954) and Bailey ( 1956) have recen ti y discussed the basic concept of subspecies in fishes with considerable clarity and reason, and they have cast doubt, not only upon the validity of a number of existing subspecies designations (sorne of the doubtfully subspecific forms being found in the Tamesí), but also upon the con­cepts on which many of the old subspecies were erected. For reasons best expressed by these authors no subspecies designations are given in the present paper. Future work is re­quired to determine the nature and extent of variation in the local populations, their divergence from other such populations, the clinal nature of such divergence, and the extent to which this may be due to environmental factors. Invalid manuscript designa­tions which have escaped into the literature with unfortunate frequency are, of course, no! employed here. A number of the fish species listed herein were first described in the monumental work of Cuvier and Valenciennes (1828--49). As noted by Bailey (1951) the authorship of all such species can and should be determined. In the present work only the appro­priate single author is given for each of these species. MATERIALS AND METHODS Material for the present study was collected during three trips to Mexico in the period 1950-53. The first trip was accomplished April 1-June 7, 1950, the second March 13­June 16, 1951, and the third December 20, 1952-January 3, 1953. Thus, a total of six months was spent in Mexico during the spring, early summer, and winter seasons. Most of the fish collections were made with a 20 or 40 foot (% inch mesh) minnow seine with native help and represent shallow upstream habitats. On the last trip a 150 foot (%, inch mesh) bag seine was taken and successfully employed in sorne of the larger waters. Additional specimens were taken by fyke net, hook, spear, minnow trap, gill net, and plastic window screening. Considerable time was spent observing the habitat dis­tribution and behavior of fishes, especially in the crystal clear waters of the upper stretches of the Río Sabinas. Such observation was particularly important in relation to groups which normally inhabit the deeper waters and such wary species as the cichlids which make frequent use of shallow areas but which are difficult to capture by seine. Most of the preliminary identifications were carried out by the writer. Robert R. Mil· ler of The University of Michigan Museum of Zoology and the late Myron Gordon of the American Museum of Natural History checked the preliminary identifications on a number of the fishes, but final species determination on almost all specimens was accomplished by Car] L. Hubbs. Food analyses were carried out essentially in accordance with the procedure previously outlined by the writer (Darnell, 1958) . In order to pro­vide a generalized picture of the true food relations of each species, specimens for food analysis were picked from severa] size classes of both sexes taken at different localities in day and night collections. Where this was not possible it was approximated. COLLECTION AND DISPOSITION OF SPECIMENS During the field work a total of 11,043 specimens of fishes were taken from the Río Tamesí drainage in seines, fyke nets, and minnow traps. About a dozen additional speci­ mens were procured by other means. In ali, 66 collections were made in the various por­ tions of the drainage as follows: Río Sabinas and tributaries 54 ( reduced to 31) collec­ tions (6,768 specimens), Río Frío and its tributary, the Río Boquilla, six collections (2,538 specimens), Río Man te and its tributaries, four collections ( 1,272 specimens), Río Guayalejo, a single collection (221 specimens), and the Laguna de Chairel at Tampico, a single collection (244 specimens). By far the greatest attention was paid to the fishes of the Río Sabinas where the general ecological study was in progress, and in order to reduce the number of stations for presentation here the data for many ad­ jacent collections were lumped. Due to lack of time, gear, and transportation facilities the fishes of the larger streams as well as the coastal lagoons around Tampico were very inadequately sampled. In addition to the collections mentioned above, the writer has examined most of the material taken by Meek in 1903 from the Río Guayalejo, but specimens reported from the Tampico area by Jordan and other early workers have not been seen. Most of the 1950-51 material has been deposited in the Chicago Natural History Mu­ Fishes of the Rw Tamesí seum. Poorly preserved specimens of the common species were discarded. For the re· maining collections, specimens of a given species taken from the same stream during the same year have been lumped and have received a single (CNHM) catalog numher. Representative specimens from the 1950-51 material are also heing deposited in the fish collections of the Zoology Department of the University of Minnesota, the Instituto de Biología, Mexico City, and the writer's prívate collection. The 1952-53 material has heen deposited in its entirety in the Tulane University (TU) collections. For the most part each field collection was kept distinct at Tulane, but in several cases nearly identical collections made the same day were lumped. History The history of ichthyofaunal investigation of the Río Tamesí area may be divided into two overlapping, but basically distinct, periods, the period of description and the period of synthesis. The first, from 1901to1908, was marked by the appearance of three major taxonomic works (Jordan and Snyder, 1901; Meek, 1904; and Jordan and Dickerson, 1908). The second, although foreshadowed by two papers of Regan (1905, 1913), really began in 1926 with Hubbs' study of sorne of the poeciliid fishes of the drainage system, and it has continued on an intermittent basis until the present time. This second period is characterized by the systematic analysis of species and genera which may extend into the area, especially from the north, but, for the most part, such studies have dealt only incidentally with the fishes of this drainage. lt may fairly be stated that, after a flurry of early attention, the ichthyofauna of the Río Tamesí has lain, nearly forgotten in the literature, for half a century. The first reference to the fishes of the Tamesí area appears to have been that of Duméril (1870) , who reported the alligator gar from Tampico. Jordan and Snyder (1901) published on fish collections from headwaters of the Río Pánuco (Río Verde near Rascón), listing several species which have subsequently been reported from the Río Tamesí. They also included several species from the vicinity of Tampico including gars and catfishes obtained in the local fish market. Shortly thereafter, S. E. Meek (1904) published an extensive monograph on the fresh·water fishes of Mexico north of the Isthmus of Tehuantepec, which included the first direct information on fishes of the headwaters of the Tamesí system. In a single collection from the Río Guayalejo at For­lón, Meek recognized 16 species including four which were described as new. Meek also provided further collections from the headwaters of the Río Pánuco (Rascón, Valles, Río Verde). lncluding those which had previously been reported from the Tam· pico area, Meek's collection brought the number of species recognized from the Tamesí to 21. In 1908 Jordan and Dickerson published an important work on the "marine" species collected from Vera Cruz and from "the muddy estuary of the Río Pánuco and elsewhere along the sandy shores." Many of these specimens must have been taken from brackish water (see Station 9A). In this paper the authors listed 28 species from the Tampico area and included one without locality data which may have been taken from Tampico. Twenty-four had not previously been recorded from the area. Most of the "marine" species listed by these writers are known to be either frequent inhahitants or, at least, occasional visitors in water which is fresh or nearly fresh, and a number of them have heen taken in the present study from thc headwaters of the Tamesí or from the nearly fresh Laguna de Chairel at Tampico. The British ichthyologist, C. Tate Regan, in 1905 puhlished the first of four papers relating to the fishes of the Pánuco.Tamesí system. In this initial work he attempted to clarify the cichlid fishes of the cÍrainage, and he reduced to synonomy one of the species descrihed by Jordan and Snyder (1901) and listed doubtfully by Meek (1904). In 1908 Regan described a new species of cichlid on the basis of two specimens which were said to have been taken from the vicinity of Tampico. In the same year he com­pleted the ichthyological section of the monumental Biología Centrali-Americana (Re­gan, 1906-1908). Although this work was concerned chiefly with the Central American fauna, six of the Pánuco-Tamesí species were mentioned. In his last paper of importance in relation to the fishes of the area, Regan ( 1913) attempted to straighten out the taxon­omy of certain of the poeciliid fishes, especially by means of the detailed characteristics of the remarkable gonopodium of the males. In this study Regan also extended the known range of the Amazon molly to the Tampico area on the basis of misidentified specimens. The second period of ichthyological work relating to the fishes of the Tamesí area has been dominated by Car! L. Hubbs. In his publications on the fishes of eastern Mexico he has cleared up numerous taxonomic problems and has aided in relating the fauna of the Pánuco-Tamesí system to that of other areas. In 1926, having reexamined Meek's early collections from the Pánuco-Tamesí drainage, Hubbs described therefrom three new species of the genus Gambusia, two of which were present in the Forlón material, and the third of which has appeared in collections from the Tamesí by the present writer. In his paper on the catostomid fishes of eastern North America, Hubbs (1930) reduced Meek's nominal species of sucker to the synonomy of a wide-ranging species from the southern United States. In his 1936 paper on the fishes of the Yucatán peninsula Hubbs discussed severa! of the species which had been recorded from the Tamesí, and he pointed out that the ariid catfish obtained by Jordan and Dickerson (1908) from Tam­pico was, in reality, G. felis, a widespread estuarine species. In 1937 and 1940 Hubbs published on the fish fauna of streams north of the Tamesí area, discussing a number of the Tamesí species. In a series of papers (C. L. Hubbs, 1933, 1934, 1955; C. L. Hubbs and L. C. H ubbs, 1932, 194-0) the same investigator, twice co-authoring with his wife, analyzed the unusual breeding behavior of the "double crossing" Amazon molly, a species which he noted to be present in the Tamesí, and in 1932 they mentioned receiv­ing live specimens of this fish from Forlón, the site of Meek's early collection. Finally, in 1954 Hubbs reduced one of the minnows of the Tamesí drainage to the synonomy of a wide·ranging northern shiner. The late Myron Gordon carried out numerous studies on the genetics and ecology of the poeciliid fishes of the Río Papaloapan in Vera Cruz, and a number of his papers refer to species which inhabit the Río Tamesí orto their close relatives (for bibliography see Gordon, 1947). Hubbs and Gordon (1943) and Gordon (1953) discussed the sys­ternatics and ecology of the xiphophorin fishes of the Río Pánuco, providing information on species which also inhabit the Tamesí. In 1947 the Mexican ichthyologist, Fernando DeBuen, published a catalog of the Ne­arctic fishes found on Mexican soil, in which he outlined the zoogeographic provinces of Mexico, listing the drainages, and sketching the ichthyofauna of each. Announcing his intention of continuing the series with a detailed discussion of each faunistic region, 30:1. Fishes of the Rí.o Tamesí he proceeded to characterize the 2'\earctic fauna. Much of this discussion bears directly upon the fauna of the Pánuco-Tamesí system, but unfortunately, with DeBuen's move to South America the series has apparently been abandoned. Another Mex.ican ichthyologist. José Ah-arez, after visiting various libraries, museums, and laboratories in the United States, published in 1949 a historical résumé of the ichthyological work accomplished in Mexico up to that time, and this was followed (1950a) by a ta.-xonomic bibliography of the Mexican fresh-water ichthyofauna. Both of these papers have been importan! aids in the preparation of the present manuscript. Aharez 11950b) al50 published a compilation of taxonomic keys to the fishes of the Mexican continental waters. Although this work brings together a great deal of scat­tered literature. it was critically re,·iewed by Miller ( 1951), who pointed out numerous errors and oversights. Other investigators whose works are of importance in the under­standing of the taxonomy or distribution of species inhabiting the Río Tamesí or the coastal lagoons indude the following: Baughman and Springer (1950), a shark; Dar­nell fl953. 1955, 1956), rnrious headwater species; Ginsburg (1931, 1932, 1933), severa! gobies: Hildebrand (1955). a croaker and a sheepshead; Clark Hubbs and Brown (1956). a minnow; and Miller (1955, 1959). cyprinodontid fishes of the genus Fundulus, as well asan eleotrid. The excellent but unpublished thesis of Curran (1942) contributes to the understanding of the gerrids. Geography and Geology The Río Tamesí system is located in east-central Mexico a few kilometers south of the Tropic of Cancer in the northern sector of the Tampico Embayment. This embayment is an allm·ial plain which slopes gently eastward from the Sierra Madre Oriental to the Gulf of i\lexico. Its width ,-aries from 100 to 150 kilometers, and its height al the foot of the mountains average;; around 100 meters above sea le\·el. Immediately west of the area rise the rugged front ranges of the Sierra Madre Oriental. and to the north lie a series of complex dipping anticlines and basalt mesas 1see Fig. 1). The geology of the Tampico Embayment area has been discus..."t'd by Muir 11936) and Heim (1940). At the present time the front ranges of the Sierra Madre Oriental consist of parallel north-south anticlinal ridges separated by shallow synclinal rnlleys. They rise abruptly from the coastal plain, and west of the embayment they reach an altitude of over 1300 meters. In the northern sector of the embayment the front range is broken by the valleys of the Ríos Guayalejo and Boquilla. both tributaries of the Río Tamesí. Waters of the Río Tamesí enter the Gulf of Mexico near Tampico. which is located about midway between the Río Sota la .\farina, on the north. and the Río Tuxpan, on the south. The Soto la i\farina and the Tuxpan are about three hundred kilometers apart, and the inten·ening coastline is very regular. Between Tampico and the Soto la Marina lies a narrow sandy strip punctuated with coastal lagoons. South of Tampico the Laguna Tamiahua lies inside the coastal strip of sand dune;,;. This large lagoon extends about two-thirds of the way to the Río Tuxpan and is apparently connected with that river by a narrow southward extension. In the lowland immediately west of Tampico lies an ex­tensi,·e series of marshes and shallow lagoons. Precipitation Rainfall in the Tampico Embayment area is markedly seasonal and varies in relation MAP 1 TAMPICO EMBAYMENT AREA SHOWING PANUCO·TAMESI DRAINAGE SYSTEM 1 LL[ft.& ARIO GUAYALEJO l.[NCINO 1 ftlO SABINAS 3.JOYA DE SAL.Al C. ftlO '""º s• 4. I OMU F"AR IAS 0 . RIO IOOUILL.A S.XICOTCNC.&TL [ ftlO MANT[ l. CHAMAL F. LAG UNA O[ CHAl"l'.L 'P.IL LIMON --· -uutovo. l .MANTt t .MAOllCATZIN ::if~) MAJ!SH IO. TAM,ICO + 11 . YALLEI O 5 10 30 40 IZ. ,ORLON ' o 1 -\, " ;¡ .. a ... ........ .. .. o _, :> .. ' ' MEXICO .Frc. l. Tampico Embayment area showing the Pánuco-Tamesí drainage system (lnset depicts the general location of the area below the Tropic of Cancer in southern Tamaulipas, 'Mexico.) Note the limited extent of the drainage during the dry season. Only the larger arroyos of the wet season drainage are shown. This figure is a composite based upon severa! maps of the area, and since ali have been found to contain many errors in detail, the composite may reflect such inaccuracies except in areas of most intensive study. to the local physiography. In late spring, summer, and early fall easterlies from the sub­lropical high belt bring moisture from the Gulf of Mexico. Passing inland these winds meet no major barrier until they reach the eastern front of the Sierra Madre. Here they rise, and, cooling, drop their moisture. Thus, although most of the embayment proper receives little direct rainfall, the precipitation increases sharply as the mountains are ap­proached, and the average rainfall of the front ranges has been estimated to be about 2,000-2,500 mm annually (Darnell, 1953). The wettest months are June and Septem­ber. ..... .i ~ e... z ... IC o ... IC o e 2 e IC IC... "' MAP 11 COHTOUR MAP OF UPPER TAMPICO EMBAYMENT ............ A.INCtNO llllie lai•H ' ·'º"Yl:Jruft e.u UNION 11.A,,•r• 1111 ci•• c . .,,.,. leru O. ITO•MI •&NCM 1 . fttCO Dr. O•O ...""ª" •• la•lll9 .......,.....,.,..... ~: :g:u'.zr:1attt1.1 f.lr.t1•ti " Oitd1 M. XICOTINCATL ....Mi-'IM• 9' 1111• ....... .1 .-IL Ll llllO N l . CH AIUL 1 • llt .lllANTI F1G. 2. Contour map of the upper Tampico Embayment area. Note relationship of headwater streams with the Sierra Madre. Details of the Río Sabinas and the Arroyo Encino should be accurate, but smaller features of the other streams should be accepted with caution. Contour intervals are given in meters. Drainage The Tampico Embayment is drained, in the south, by the Río Pánuco and, in the north, by the Río Tamesí which join shortly before entering the Gulf. Severa! tributaries of the Río Pánuco originate in the high central plateau of Mexico and traverse the Sierra Madre Oriental in spectacular cascades and waterfalls. Others arise as large springs or "nacimientos" (= birth) fed by underground rivers from which blind cave fish are known. Among the tributaries of the Río Tamesí, only the northernniost, the Guayalejo, begins high in the mountains. The remainder arise as small springs or large nacimientos in shallow valleys at the foot of the Sierra, and they lie almost entirely within the Tampico Embayment. Quite different in details of origin, the Ríos Guayalejo, Sabinas, Frío, Boquilla, and Mante join, one by one, to form the Río Tamesí which meanders coastward (see Fig. 2). Río GuAYALEJO The northernmost tributary, the Río Guayalejo, is born high in the Sierra Madre in the synclinal valley of Juamave. After traversing the Sierra through a narrow canyon, the stream then bends southward into the northern edge of the Embayment. In its low­land portion the Guayalejo contains numerous deep pools •and exhibits modest flow during the dry season, but the broad bed and steep banks attest to a greatly increased flow volume during the rainy season. As in the case of the other streams of the Tamesí drainage, the Río Guayalejo receives numerous arroyos which provide rapid surface drainage during times of heavy precipitation, but which during the dry season may ex­hibit reduced flow, isolated pools, orno water at all. Proceeding southward through the embayment the Guayalejo receives in turn the Ríos Sabinas, Frío, and Mante before heading coastward as the Río Tamesí. Río SABINAS The Río Sabinas, the second tributary, takes origin in a rocky canyon at the foot of the Sierra Madre about 13 kilometers north of Gomez Farías. The Nacimiento of the Sabinas is a limestone basin filled with water to a depth of 18 meters and has an esti­ mated surface area of a little less than one acre. This basin is fed by an underground river, and during the dry season the Río Sabinas, as it leaves the Nacimiento, exhibits a flow volume estimated at several cubic meters per second. Below the Nacimiento for three or four kilometers the Río Sabinas traverses a narrow, winding, rocky canyon where the current is generally swift and where habitat conditions are highly variable. Leaving this canyon it continues southward paralleling the base of the Sierra, and here it is characterized by longer pool areas and less abrupt habitat transiticms. About six kilometers below the Nacimiento, at Storms' Ranch, the Río Sabinas receives one of its major tributaries, the Arroyo Encino. Below the ranch the river continues southward to about the level of Gomez Farías where it abandons the mountains and swings east­ ward. Beyond this point riffies are less prominent, and the river continues as a sluggish stream past the Mexico-Laredo highway to its junction with the Río Guayalejo at Ad­ juntas. Below the highway bridge the Sabinas passes into a shale exposure. As seen at Adjuntas this shale produces a deep fine powder which, during the dry season, coats ali the surrounding landscape, including the vegetation. In the Sabinas this material forms a deep powdery silt-like bottom and imparts to the warm sluggish water a tawny, turbid appearance. No fish collections were attempted here, although certain of the more tolerant species collected in the Río Guayalejo opposite the mouth of the Sabinas may also be present in the lower portion of the Sabinas itself. This lower stretch of the Río Sabinas undoubtedly serves as an effective barrier to the dispersa! of headwater fishes, at least during the dry season. Major tributaries of the Río Sabinas include the Arroyo La Flor and the Arroyo En­ cino. The former lies in the rocky canyon above the Nacimiento of the Sabinas, and dur­ ing the rainy season its waters enter the Sabinas at the Nacimiento. Although this ar­ royo was not visited during the wettest season, ample evidence indicated that following heavy rains it contains a torrential stream which may achieve an average depth of two or three meters. In the dry season its bed exhibits a chain of spring-fed ponds connected with each other and with the Nacimiento by a slight current. Sorne of the connections are subsurface, and all probably act as barriers to interpond dispersa} of the fishes. The Arroyo Encino begins as a series of small springs at the village of Encino on the Mexico-Laredo highway about eleven kilometers northeast of Gomez Farías. After me­andering through the scrub forest for about five kilometers this arroyo joins the Río Sabinas at Storms' Ranch. Due to the presence of the springs, this arroyo contains pools connected throughout the dry season by small, flowing rifHes. lt receives one major tributary, the Arroyo Sarco, which during the dry season supports only a series of dis­connected or slightly connected ponds. Río Fruo The Río Frío begins at the foot of the Sierra a short distance south of Gomez Farías. Although not visited by the writer, the Nacimiento of the Río Frío is said to consist of a series of small springs whose combined flow during the dry season is considerahly less than that of the Río Sabinas. Like the Sabinas, however, the Río Frío passes southward for severa} kilometers, and then swinging to the southeast it leaves the mountains to join the Río Guayalejo. Two or three kilometers above its junction with the Guayalejo and about twenty-five kilometers from its source the Frío receives its m:.jor tributary, the Río Boquilla. Below this junction the Frío is a large, turbid, sluggish lowland stream. As in the case of the lower sector of the Río Sabinas, the lower stretch of the Río Frío undoubtedly actsas a habitat barrier to the dispersa} of upstream fishes. The Río Boquilla drains the valley of Chama} severa! kilometers southwest of Gomez Farías. Although a few springs are found in the headwaters of the Boquilla, most of the arroyos as well as the upper portions of the Río Boquilla itself are devoid of current in the dry season. During the course of the present work a small shallow lake was en­countered in the Chama} valley, and there is evidence that lake conditions were much more extensive in this valley in the past than at present. After leaving the Chama! Valley through a narrow breach in the low El Abra ridge, the Río Boquilla passes southeast­ward to its junction with the Río Frío. Río MANTE The Río Mante flows as a large stream from a cave in the eastern face of the El Abra ridge about eight kilometers southwest of Ciudad Mante. Four or five kilometers from the source a dam has been placed across the river creating a reservoir which apparently extends ali the way back to the Nacimiento. Diversion canals remove water from the reservoir just above the dam, and by means of open ditches they distribute this flowing water throughout the countryside primarily for irrigation purposes but also for human consumption. lmmediately below the dam the bed of the Río Mante, deprived of most of its water supply, contains during the dry season a series of pools in the pavement limestone. A few hundred meters downstream, however, the Río Mante takes on the as­pect of a small headwater stream and consists of small rocky pools with alternating rif­fles. Possessing little flow during the dry season the Río Mante soon becomes polluted, and in the immediate vicinity of Ciudad Mante the river is one long, heavily-polluted pool. Near the junction of the Río Mante with the Río Guayalejo, as shown on various maps of the area, the adjacent land apparently becomes low and swamp-like. This swampy area has not been 'investigated in the present study. Río TAMESÍ After receiving the headwater tributaries the Río Tamesí meanders caastward, joined here and there by dry arroyos. Although it is bounded by high steep banks, it is a slug­gish lowland stream during most of the year. Nearing the coast the river passes •a series of marshes and lagoons which are rather extensive, even during the dry season. Sixteen kilometers inland, after traversing the Laguna de Chairel, the Tamesí joins the Río Pánuco, and they flow to the Gulf as a single river. This area has been well described by Jordan and Sny'der (1901) as follows: "At Tampico the Pánuco, a very large river, receives the Río Tamesoe. With the two, a number of large, shallow lagoons are con­nected. Salt tide water backs up into the rivers and lagoons for sorne distance above the city. The lagoons are marshy in most places, the rushes and shrubs growing out into the water for a long distance. The bottom and shores are usually of a sticky blue clay, although there are sandy beaches in sorne localities." As pointed out previously, brackish­water coastal lagoons are also found ·along the Gulf coast for sorne distance both above and below the mouth of the Pánuco-Tamesí river system. Collecting Stations in the Río Tamesí System Río SABINAS Series l. Arroyo Encino series from springs at Encino, where the arroyo begins, to its junction with the Río Sabinas at Storms' Ranch (7 km northeast of Gomez Farías). Station lA. April 20, 1951. R. M. Darnell and natives (field no. E-1). Small upper spring above village of Encino ( about 100 m east of the Mexico-Laredo highway). Water clear, current moderately slow; spring about 2 m across, % m deep; bottom of sand and shale; no vegetation; shaded. Fishes collected by seine, and estimated half of resi­dent population taken. CNHM colls. Station lB. May 22, 1951. R. M. Darnell and natives (field no. E-9). Repeat of collection lA after week of heavy rains. CNHM colls. Station lC. April 20, 1951. R. M. Darnell and natives (field no. E-2). Second small spring above village of Encino and upper 15 m of creek. Water clear, current moder­ately slow; creek 1 m wide, 0.14 m deep; bottom of shale and mud; little vegetation in water; partly shaded. Fishes collected by seine, and estimated half of population taken. CNHM colls. Station ID. April 20, 1951. R. M. Darnell and natives (field no. E-3). Lower 15 m of creek ( down to its junction with the bed of the Arroyo Encino) above the village of Encino. Water clear, flowing; rock and mud bottom; O-% m in depth; shaded by broad­leaved emergent plants (Xanthosoma robustum) growing in the water. Fishes collected by seine, and estimated one-fourth of population taken. CNHM colls. Station lE. April 20, 1951. R.M. Darnell and natives (field no. E-4). Pool of Arroyo Encino at mouth of spring creek above village of Encino. Water clear, current imper­ceptible; two bottom types evident: 1) rocks carpeted with filamentous algae and fioc­culent organic material ( inhabited only by M. sphenops), and 2) exposed mixed bottoms of rocks, gravel, and sand (frequented by both M. sphenops and G. regani); pool about TABLE 1 Fishes collected in the Arroyo Encino and Arroyo Sarco Arroyo Encino Arroyo Per cent IA IB IC ID !E IF !G iH 11 lJ IK IL IM IN Sarco 2A oí total Astyanax /asciatus 41.7 16.0 6.8 9.9 8.0 26.7 30.2 21.6 Dionda rasconis 1.2 '17.4 54.0 '18.4 19.8 2.4 15.7 Diondasp. 1.4 1.2 6.7 2.3 Notropis sp. 0.6 8.9 2.8 Jctalurus australis (40.0) 0.1 Gamhusia regani 27.3 11.5 60.0 '22.9 1.2 10.6 1.7 0.6 1.2 3.9 3.9 Gambusia vittata 21.5 31.9 15.8 9.5 Mollienesia sphenops 18.2 69.2 40.0 71.4 33.3 43.2 54.5 7.2 '26.4 13.7 43.4 30.0 Xiphophorus variatus 100.0 5'41.5 19.2 5.7 14.8 10.6 1.4 8.6 2.4 ('100.0) 0.7 4.0 Cichlasoma cyanoguttatum 25.0 22.2 2.2 'l.2 'l.6 (20.0) 9.1 4.8 Cichlasoma steindachneri 1.2 ('100.0) 0.8 3.1 3.2 ('20.0) 10.4 5.2 Gobiomorus dormitor pv pv (20.0) 0.1 Total no. in collection 9 11 26 5 140 12 81 132 (4) 36.3 163 899 (ca.12) (5) 1,008 2,870 Fi~ure1 repreaent the percenlage composition of each collcclion. Bottom lolals give numbers of fishea in each collection. Fi11hes nol collected by 1eine are placed in parenthcaes. Sight recorda are recorded by the letter ºp", and i( lhe ob11ervation was lattr verified by specimen1, il is marked .. pv". Certain fishee taken by hook and 1pear are not included in the table but are discussed in the text. 6 m across and 1/s m in depth; exposed, much sunlight. Fishes collected by seine, and estimated one-fifth of population taken. CNHM colls. Station lF. May 22, 1951. R. M. Darnell and natives (field no. E-10). Uppermost deep pool of Arroy·o Encino at village of Encino (adjacent to and on both sides of bridge of Mexico-Laredo highway). Sorne human sewage in water. Dangerous collecting ! Water turbid (black dueto decomposing organic pollutants), no current; bottom of deep black mud containing much broken glass, cans, and other trash; 0-11/2 m in depth; partly shaded. Fishes collected by seine. CNHM colls. Station lG. May 22 , 1951. R. M. Darnell and natives (field no. E-11). Arroyo of Encino 200 m below bridge of Mexico-Laredo highway. Much sewage from village of Encino floating in water. Water very turbid, no current; bottom deep organic ooze; 0-1 m in depth; enormous quantites of algae in water (chiefly Spirogyra, but also in­cluding Merismopoedia, Oscillatoria, Mougeotia, Ulothrix, and Closterium); many ex­ogenous leaves and branches in water; partly shaded by moderately dense bank vegeta­tion. Fishes collected by seine. CNHM colls. Station lH. May 8, 1950. R.M. Darnell and natives (field no. Sa-8). Pools in Arroyo Encino 200-400 m abo ve j unction with Río Sabinas (at least 3 km downstream from Station lG). Water slightly turbid, current very slow; rocky bottom carpeted with sorne mud and much flocculent organic material ( containing diatoms, filamentous algae, and decomposing vegetation); depth 0-1 m; sorne vegetation in shallows; partly shaded; arroyo bed deep here, bank steep and heavily vegetated on north side, low and sparsely vegetated on south side. Fishes collected by seine. CNHM Colls. Station 11. April 17, 1951. R.M. Darnell and natives (field no. E-5). Pool in Arroyo Encino 200 m above junction with Río Sabinas. Habitat data same as for Station lH. Observations on apparent nest-building behavior of C. steindachneri. Fishes collected by length of gill net emplc>yed as seine. CNHM colls. Station lJ. May 2, 1950. R.M. Darnell and natives (field no. Sa-7). Pools in lower 200 m of Arroyo Encino at junction with Río Sabinas. Habitat data approximately' as in lH, although pools slightly deeper, and the mouth of the Arroyo is essentially a long, deep, quiet backwater of the Río Sabinas. Steep banks were densely vegetated. Fishes collected by seine. CNHM colls. Station lK. April 28, 1950. R. M. Darnell and natives (field no. Sa-4). Same as lJ except that only lower 150 m of Arroyo were included. Fishes collected by seine. CNHM colls. Station lL. December 21, 1952. R. M. Darnell, J. H. Darnell, and E. Liner (field nos. X-2, 3, 4, 5, 6). Repeat of lJ, except that sorne gravel riffies were included. Fishes collected by seine. Mus. nos. TU 5574-83. Station lM. January 2-3, 1951. R. M. Darnell (field no. X-30). Collection made in backwater behind log in second pool above mouth of Arroyo Encino. Live fishes (X. variatus only) collected in overnight set of a glass minnow trap. Fish brought back ali ve for experimentation. Station IN. January 3, 1951. R. M. Darnell (field nos. X-29, 31). Mouth of Arroyo Encino. Conditions as described in lJ. Fishes collected by fyke nets. Mus. nos. TU 5691-94. Series 2. Arroyo Sarco (tributary of Arroyo Encino). Pond series about 2 km northeast of Storms' Ranch. Fishes of the füo Tamesí Station 2A. December 23, 1952. R. M. Darnell, J. H. Darnell, and E. Liner (field nos. X-7, 8, 9, 10, ll). Collections made from a series of ponds connected by a small trickle of water which disappeared underground at the lower pond. Water clear; bottoms variable, rock, mud; 0-1 m in depth; sorne ponds with much emergent vegetation, others with thick ftoating mats of filamentous algae; shore composed of exfoliating shale and surrounded by scrub vegetation. Fishes collected by seine. Mus. nos. TU 5584-90. Series 3. Arroyo La Flor. Pond series from Nacimiento of Río Sabinas north in the arroyo for about % km. Conditions variable from one pond to another and from one season to another within a given pond. Station 3A. January 1, 1953. R. M. Darnell, J. H. Darnell, and E. Liner (field no. X-28). Uppermost (6th) pond above Nacimiento of Río Sabinas. Water clear, basin rocky; 0-2 m in depth; little aquatic vegetation except algae carpeting sorne rocks; shore rocky and slightly wooded. Fishes collected by seine. Mus. nos. TU 5686-90. Station 3B. December 24, 1952. R. M. Darnell, J. H. Darnell, and E. Liner (field nos. X-16, 17, 18). Upper ( 4th and 5th) ponds and broad, shallow, interconnecting rifile above Nacimiento of Rfo Sabinas. Water mostly clear; basin of rock and grave!; 0-1 m in depth; much matted green algae, especially in rifile, rocks coated with algae; shore a rocky beach with occasional trees. Fishes collected by seine. Mus. nos. TU 5603-07. Station 3C. December 23, 1952. R. M. Darnell, J. H. Darnell, and E. Liner (field nos. X-13, 14, 15). Lower (lst, 2nd, and 3rd) ponds above Nacimiento of Río Sabinas. Water clear, slight current; basin of limestone rock and boulders; 0-1 m in depth; rocks coated with algae; shore of rock and boulders. Fish collected by seine, but one large catfish (1. australis) sought shelter in crevice under boulder and was extracted by hand. Mus. nos. TU 5594.--5602. Station 3D. April 29, 1951. R. M. Darnell and natives (field no. E-7). First pond above Nacimiento of Río Sabinas. Water clear, without perceptible current (the fishes had probably been isolated for 5-6 months previous); 0-1 m deep; basin of limestone bedrock; sorne algae coating rock; shore of rock and boulders. Fish collected by seine. CNHM colls. Series 4. Río Sabinas-river series from Nacimiento to junction with Río Guayalejo. Station 4A. April 30, 1950. R. M. Darnell and natives (field no. Sa-6). Former bed of Río Sabinas which forms a long, shallow extension of the Nacimiento (est. 40 m X 4 m) parallel to Río Sabinas at its origin and connected with Río Sabinas for about 10 m. Water clear, current modera te in i~itial 10 m, but virtually absent in remaining pocket; basin of limestone and conglomerate rocks, mostly covered by silt, mud, or ooze; depth 0-1 m; rooted aquatic plants and algae mats abundant; shore rocky and exposed. Fishes collected by seine. CNHM colls. Station 4B. April 29, 1951. R. M. Darnell and natives (field no. E-6). Repeat of 4A. Fishes collected by seine. CNHM colls. Station 4C. December 23, 1952. R. M. Darnell, J. H. Darnell, and E. Liner (field no. X-12). Repeat of 4A. Fishes collected by seine. Mus. nos. TU 5591-93. Station 4D. April 13, 1950. R.M. Darnell and B. E. Harrell (field no. Sa-3). Shallow backwater of Río Sabinas 200 m upstream from Storms' Ranch. Water slightly turbid, no current; bottom of rock, gravel, sand, and silt, generally covered with a layer of organic detritus; depth 0-1/2 m, but mostly less than 5 cm; shallow water heavily coated TABLE 2 Fishes collected in the Arroyo La Flor and Río Sabinas (For explanation see Table 1) Arroyo La Flor Rfo Sabinas 3A 38 3C 3D 4A 48 4C 4D 4E 4F 4G 4H 41 4J 4K 4L Per cent of total Astyanax fasciatus 16.2 17.7 22.3 62.3 60.2 49.8 '11.4 6.8 22.0 14.4 15.4 1.4 62.7 3.6 '13.3 3.4 20.7 l ctiobus bubalus (?) p p p Dionda rasconis 78.2 53.S. 13.8 0.4 35.3 26.6 15.2 15.4 86.4 19.6 31.0 47.1 28.2 27.0 Diondasp. 1.5 2.5 7.2 2.9 1.9 0.7 Notro pis lutrensis 0.7 2.0 2.9 15.3 1.4 Notropis sp. 6.0 2.4 2.0 1.0 '1.5 0.5 lctalurus australis 0.1 p pv pv pv 0.1 Gambusia regani 0.5 0.9 l.9 1.7 15.2 15.4 2.8 2.4 3.8 l.s. Gambusia vittata 34.6 36.'l 25.6 11.4 '13.7 35.7 '20.0 40.1 11.3 Mollienesia sphenops 3.5 8.6 61.6 25.4 11.7 7.7 77.'l 9.0 2.9 20.0 38.5 6.0 1.0 3.4 28.7 Xiphophorus montezumae 0.1 0.9 26.2 19.6 0.8 2.0 Xiphophorus variatus O.'l 2.9 4.3 0.8 0.5 Agonostomus monticola (?) p p p p p p p Cichlasoma cyanoguttatum 0.7 0.5 0.5 10.5 p 7.7 p 1.7 p 0.5 1.2 Cichlasoma steindachneri l.4 19.7 1.0 13.2 11.4 6.8 4.6 15.4 2.0 18.7 4.8 l.5 4.6 Gobiomorus dormitor p pv 0.4 0.1 Total no. in collection 1'42 198 1,481 114 103 235 70 133 241 125 13 280 91 252 210 282 3,910 ( ?) =:reeords in need of verification (see lexl) . Fishes of the füo Tamesí with floating mats of filamentous green algae; bank heavily vegetated on one side,..partly shaded. Fishes collected by seine. CNHM colls. Note: Day and night observations as well as collections made by hook and spear in adjacent deep water indicated the presence of severa! species not captured here in the seines. These are indicated simply as present (p). On May lOth a y'oung Fer-de-lance, Bothrops a,J,rox (130 cm), was captured about fifty meters downstream from this station on the heavily vegetated riverbank two meters from the water's edge at the terminus of a trot line. This marks the approximate nortbern limit of distribution of this deadly snake. Station 4E. April 28, 1950. R. M. Darnell and natives (field no. Sa-5). Río Sabinas at Storms' Ranch. Entire downstream edge of long pool which receives mouth of Arroyo Encino. Collections made at night (9:30-10:30 p.m.). Water slightly turbid, slight current; mixed bottom of rocks, grave!, sand, silt, mud, and ooze; depth 0-1% m, col­lections made through a thick growth of vegetation, mostly Potamogeton; bank exposed. but no light at night. Fishes collected by seine. CNHM colls. Station 4F. December 21, 1952. R. M. Darnell, J. H. Darnell, and E. Liner (6eld no. X-1). Repeat of 4E except that collections were made during afternoon. Fishes col­lected by seine. Mus. nos. TU 5567-73. Station 4G. April 2 1950. R. M. Darnell and natives (field no. Sa-1). Río Sabinas at Storms' Ranch, 200 m downstream from 4E. Collections made at edge of pool just below extensive riffie. This collection represents normal condition at the end of the dry season. Water clear, edge of moderate current; bottom of sand, rock, and gravel; depth 0-1 m; vegetation absent; water shaded. Fishes collected by seine. CNHM colls. Station 4H. April 8, 1950. R. M. Darnell and natives (field no. Sa-2). Location same as 4G. Depth 0-15 cm. Fishes collected by means of a length of window screening. Screen was fanned just above bottom, creating a patch of turbid water, then raised to capture the fishes attracted by the suspended matter. CNHM colls. Station 41. May 12, 1950. R. M. Darnell and natives (field no. Sa-9). Repeat of 4G after series of heavy' rains. Current very swift. Fishes collected by seine and were prob­ably not in the fu]] current. CNHM colls. Station 4J. May 26, 1950. R.M. Damell and natives (field no. Sa-10). Repeat of 4G and 41 after water leve] was back to normal. Water clear, current slight; bottom heavily silted. Fishes collected by seine. CNHM colls. Station 4K. April 30, 1951. R. M. Darnell and natives (field no. E-8). Río Sabinas at Rancho Pico de Oro (3% km northeast of Gomez Farías, Tamps., Mexico). Back­water and pool collections. Water clear, edge of moderate current; hottom of sand, silt, mud with many exogenous leaves; depth 0-1 m; vegetation sparse; water shaded by trees growing on rocky beach; 100 m upstream the dense forest extends to water's edge and dense stands of aquatic vegetation are present in water. Fishes collected by seine. CNHM colls. Station 4L. January 1, 1953. R. M. Darnell, J. H. Darnell, and E. Liner (field no. X-27). Río Sabinas under bridge of Mexico-Laredo highway (km #595.5) (6 km southeast of Gomez Farías, Tamps., Mexico). Collections made from edge of long pool. Water clear; current slow; bottom varied, rocks, grave], sand, mud; depth 0-1 m; aqua­tic vegetation in part of area seined; water shaded by bridge and by high trees on floodplain. Fishes collected by seine. TU 5676-85. Series 5. Río Frío series below Nacimiento. Station 5A. Decernber 31, 1952. R. M. Darnell, J. H. Darnell, and E. Liner (field no. X-25). Pool of Río Frío at meteorological station near Nacimiento (about 6 km south of Gomez Farías, Tamps., Mexico) . Water clear, current slight; bottom mud and gravel; 0-1 m in depth; mu ch aquatic vegetation around margin; water shaded by shore trees. Fishes collected by' seine. TU 5662-68. TABLE 3 Fishes collected in the Río Frío and Río Boquilla (For explanation see Table 1) Río Frío Río Boquilla SA 6A 6B 6C 6D 6E Per cenl of total Dorosoma cepedianum 0.6 2.5 1.4 1.4 Astyanax fasciatus 19.3 5.8 2.9 15.0 2'8.7 1.8 16.4 Dionda rasconis 4.9 14.8 20.4 13.5 14.2 Diondasp. 45.7 .. .. . 3.0 lctalurus australis 1.2 '1.3 0.9 0.8 lctalurus /urcatus 1.3 0.5 Gambusia panuco 55.7 '20.7 6.2 7.4 0.8 8.2 Gambusia vittata 16.7 1.1 Mollienesia sphenops '1.2 19.'2 fB.7 59.6 2'2.9 20.5 32.5 Xiphophorus montezumae 4.8 0.3 Xiphophorus variatus 10:2 1.9 3.1 2.0 Cichlasoma cyanoguttatum ·­···· 17.3 9.8 3.1 12.6 62.0 19.5 Cichlasoma steindachneri 1.8 0.3 0.1 0.2 Total no. in collection 166 52 347 453 '1023 497 2,538 Series 6. Río Boquilla series (R. Frío drainage)-river and tributaries in Chama} valley. Station 6A. December 26, 1952. R.M. Darnell, J. H. Darnell, and E. Liner (field no. X-22). Spring pool in headwaters of Río Boquilla on Ben Gorham ranch (about 2 km west of Chamal, Tamps., Mexico). Water slightly turbid, current imperceptible; bottom mud; 0-1 m in depth; aquatic vegetation sparse; water shaded. Fishes collected by seine. Mus. nos. TU 5628---5632. Station 6B. December 26, 1952. R. M. Darnell, J. H. Darnell, and E. Liner (field no. X-21). Shallow arroyo pools in headwaters of Río Boquilla (about 2 km southeast of Chamal, Tamps., Mexico) . Water slightly turbid; current slight; bottom of mud, rocks, and grave!; 0-1/z m in depth; aquatic vegetation limited to oalgae on rocks; partly shaded. Fishes collected by seine. Mus. nos. TU 5620-27. Station 6C. December 26, 1952. R. M. Darnell, J. H. Darnell, and E. Liner ( field no. X-19). Deep pool in Río Boquilla at mouth of arroyo on }orilla ranch (6.4 km southeast of Chamal, Tamps., Mexico). Water fairly turbid, no current; bottom of mud, rocks, and gravel; 0-2 m deep; aquatic vegetation absent; water partly shaded. Fishes collected by seine. Mus. nos. TU 5608---13. Station 6D. April 5, 1950. R.M. Darnell and B. E. Harrell (field no. Ch-1). Collec· tions made at end of long, exceptionally dry season from a series of deep pools in bed of Río Boquilla on Procter ranch (3 km east of Chama!, Tamps., Mexico). Water very turbid, no current; bottom of fine silt and mud; 0-2 m deep; no vegetation, but much brush and logs in water; shaded. Fishes collected by· seine. CNHM colls. Station 6E. December 26, 1952. R. M. Darnell, J. H. Darnell, and E. Liner (field F ishes o f the Río T amesí no. X-20). Shallow lake in headwaters of Río Boquilla on ranch of Don Modesto (about 4 km southeast of Chamal). Water turbid, no current; muddy bottom; 0-11/2 m deep; vegetation scarce; exposed. Fishes collected by seine. Mus. nos. TU 5614-19. Series 7. Río Mante series, irrigation ditch and river from Nacimiento to below reservoir. TABLE 4 Fishes collected in the Río Mante (For explanation see Table 1) Irrigation diLch Río Mante 7A 7B 7C 7D Per cent of total Astyanax fasciatus Diondasp. Gambusia affinis Gambusia vittata Gambusia sp. Mollienesia latipunctata Mollienesia sphenops Cichlasoma cyanoguttatum Cichlasoma steindachneri Gobiomorus dormitor 1.0 10.3 $2.6 32.0 4.1 7.3 0.9 tfl.7 11.5 28.l 'l.'2 3.3 8.1 ·­···· 1.0 2.0 8'2.9 1.0 5.0 14.:i 1.3 13.6 24:2 0.9 42.0 3.5 0.1 pv u.o '1.6 8.3 30.7 0.6 36.5 9.8 0.3 1.3 p Total no. in collection 97 3'31 99 745 1,272 Station 7 A. June 4, 1950. R.M. Darnell and natives (field no. Ma-3). Roadside ditch and concrete culvert midway between Ciudad Mante and reservoir (about 3 km south­west of Ciudad Mante, Tamps., Mexico). Water clear, moderate current; bottom of mud and concrete; depth 0-11;2 m; vegetation dense in ditch, but limited to encrusting algae on aprons of culvert; exposed. Fishes collected by seine. CNHM colls. Station 7B. January l, 1953. R. M. Darnell, J. H. Darnell, and E. Liner (field no. X-26). Small pools and riffies of Río Mante 200 m below dam (about 4 km southwest of Ciudad Mante). Water clear, current slow; bottom of rocks, gravel, and mud; depth 0-1;2 m; vegetation absent; partly shaded. Fishes collected by seine. Mus. nos. TU 5669-5675. Station 7C. May 3, 1950. R.M. Darnell and B. E. Harrell (field no. Ma·l). Collections from edge of Río Mante 100-200 m below its Nacimiento on the Rancho Río Escondido (about 8 km southwest of Ciudad Mante). Water clear, current slow but definite; bottom of mud; depth 0-11;2 m; submerged vegetation (Myriophyllum) very dense; partly shaded. Fishes collected by seine. CNHM colls. Station 7D. June 4, 1950. R.M. Darnell and natives (field no. Ma-2). Collections from flooded beach at edge of reservoir of Río Mante, 100-200 m above dam ( 4 km southwest of Ciudad Mante). Water clear although surface covered with floating straw, no per· ceptible current; bottom of soil and grass (flooded); depth 0-11;2 m; vegetation grass and weeping willow tree branches in water; exposed. Fishes collected by seine. CNHM colls. Series 8. Río Guayalejo series-from Forlón to mouth of Río Sabinas. Station 8A. May 10, 1903. S. E. Meek (no field no.). Río Guayalejo, about 30 km southeast of Llera and about 30 km northeast of Xicotencatl. The following quotations are taken directly from Meek's field notes relating to May 9 and 10, 1903. "Went to ranch of Graham and Hudson." "River al buildings, about 50 feet below, Bottom of TABLE 5 Fishes collected in the Río Guayalejo (For explanation see Table 1) Río Guayalejo SA 88 Lepisosteus osseus Dorosoma cepedianum. Astyanax /asciatus lctiobus bubalus Dionda rasconis Diondasp. Notro pis lutrensis Notropis sp. lctalurus australis lctalurus furcatus lctalurus mexicanus Gambusia regani Gambusia vittata Mollienesia formosa Mollienesia latipunctata M ollienesia sphenops Xiphophorus variatus Cichlasoma cyanoguttatum Cichlasoma steindachneri Gobiomorus dormitor X X X X X X X X(H) X(H) X X X X X X 0.5 17.2 15.8 2.7 7.7 20.4 15.4 2.7 1.4 (?) 3.2 o.s. 7.2 4.1 0.9 0.5 Total no. in collection '.221 X=present in Meek's collection. X(H) = presence in Meek's collecLion established by Hubbs (1926). (?) =identification questionable. river stony, current swift. river varíes from 40 to 75 feet wide, Fishes not collected are the Roballo, long nosed gar, one of which 1 saw in the water, and the fresh water drum, ....."In his publication Meek (1904) mentioned that during the dry season the river was a small stream flowing over a "rocky and gravelly bed," and he further reported seeing longnose gars in "a deep sluggish creek at Forlón." Fishes probably collected by seine. Mus. nos. CNHM 4474-90, 14033-58, 15592-16647. Note: Most maps of this area show two neighboring localities with the name of Forlón, one on the railroad and the other on the Río Guayalejo about 6 km south of the first. Neither locality has been visited by the present writer. Meek's description is about what would be expected for the Río Guayalejo midway between Xicotencatl and Llera during early May, however, and since no other major tributary is known in that area with fifty foot high banks and with swift water during the dry season, it is tentatively assumed that his collecting station was located in the southernmost of the two Forlóns on the Río Guayalejo. Station 8B. December 31, 1952. R.M. Darnell, J. H. Darnell, and E. Liner (field no. X-24). Río Guayalejo at Adjuntas, across from mouth of Río Sabinas (7 km southwest of Xicotencatl). Water turbid, current moderate to swift; bottom of rock, covered in sorne places with silt; depth 0-1Y2 m; aquatic vegetation absent; exposed. Fishes col­lected by seine. Mus. nos. TU 5646--61. Series 9. Río Tamesí and lagoons around Tampico. Station 9A. Unspecific records from the Tampico area ("Tampico", "Tampico fish market", "lagoon(s) at Tampico", "lagoon near Tampico", "coastal lagoons", "lagoon near mouth of Río Pánuco", "the river") by various authors (Duméril, 1870; Jordan F ishes o f the Río T amesí TABLE 6 Fishes recorded from the Tampico area or collected from the Laguna de Chairel (For explanation see Table 1) uTampico" Laguna de Cbairel 9A 98 Carcharhinas leucas Lepisosteus osseus Lepisosteas spatula Anchoa hepsetas Anchoa mitchilli Dorosoma cepedianum Dorosoma petenense Astyanax fasciatus lctiobus buba/as Galeichthys felis lctaluras furcatas Oostethus lineatas Cyprinodon variegatus Fundulas grandis Fundulus similis Lucania parva Gambusia a ffinis M ollienesia latipinna Mollienesia sphenops Mugil cephalus Mugil curema Caranx hippos Caranx latas Lutjanas cyanopteras Lutjanas griseas Archosargas probatocephalas Eugerres brasilianas Eugerres plumieri Eucinostomas melanopterus Bairdiella ronchas Cynoscion nebulosus Micropogon undulatus Pogonias cromis Chaetodipteras faber Cichlasoma cyanoguttatum Cichlasoma steindachneri Dormitator maculatus Eleotris pisonis Gobiomoras dormitar Evorthodas lyricas Gobionellas boleosoma Gobionellus claytoni Gobiosoma bosci Citharichthys spilopterus Opsanus beta X X X (?) X X X X X X X (?) ( ?) ( ?) X X X X X X X X X X X X X X X X X X X X X X (?) (?) X (?) 0.4 15.6 23.4 0.8 0.8 0.4 0.4 2.5 4.9 36.'l 5.7 8.2 0.8 Total no. in collection 244 ( ?) ==records in need of verificalioo (see lext). and Snyder, 1901; Meek, 1904; Jordan and Dickerson, 1908; Regan, 1908, 1913). Station 9B. December 29, 1952. R. M. Darnell, J. H. Darnell, and E. Liner (field no. X-23). Laguna de Chairel at Tampico (shore of island across lagoon from Balneario Rojas). Several collections made around island including drags to the muddy shore as well as purses of seine in areas where the shore was unapproachable. Water moderately turbid, not salty' to taste ( est. 1--4 %o salinity), no current; mud bottom; depth 0-2 m; many beds of aquatic vegetation, also clear areas; shore conditions variable, including sedge mat, marsh, and mud beach; exposed. Fishes collected by severa! sizes of seines. Mus. nos. TU 5633-45. Annotated List of Species CARCHARHINIDAE-Requiem Shark Family Carcharhinus leucas (Müller and Henle). Bull shark Carcharias piatyodon (Poey) . Jordan and Dickerson ( 1908, Tampico) Carcharhinus leucas (Müller and Henle). Baughman and Springer ( 1950, Tampico) Atlantic coast of Americas from New York to Brazil; also in Bermuda and West ln­dies. The bull shark is a frequent visitor of brackish water lagoons on the northern Gulf coast (Darnell, 1958; Hoese, 1958), and it has been known to penetrate rivers as muchas 160 miles from the mouth (Gunter. 1938). Although no specimens were taken in the present study, the species is anticipated from the Tampico lagoons. The closely related C. nicaraguensis inhabits fresh water. Food habits of the bull shark on the northern Gulf coast have heen summarized by Darnell (1958), and Baughman and Springer ( 1950) have discussed breeding habits of the species. Station: 9A. LEPISOSTEIDAE-Gar Family l--episosteus osseus (Linnaeus). Longnose gar, "Aguja" Lepisosteus osseus (Linnaeus). Jordan and Snyder (1901, Tampico) Lepidosteus osseus (Linnaeus). Meek (1904, San Juan, Valles, Forlón) Eastern United States; along Atlantic and Gulf coasts from Massachusetts south to the Río Pánuco. Jordan and Snyder (1901) reported that the longnose gar was plentiful in Tampico markets and that these specimens were said to have been taken from the "river and neighboring lagoons." Although he captured no specimens of the longnose gar in the Tamesí, Meek (1904) reported seeing a number of them in a deep sluggish creek at Forlón. In the present study a single small specimen was taken from the Río Guayalejo at Adjunta~. The longnose gar is undoubtedly widely distributed throughout the deeper waters of the Tamesí drainage which have not been adequately sampled. On the northern Gulf coast the species has been taken from brackish waters (Darnell, 1958), and even though it may occur in the brackish lagoons around Tampico, it is probably not as characteristic of these lagoons as is the more euryhaline alligator gar. In the head­water tributaries the natives recognize the longnose gas as the "aguja" and state that it is an occasional visitor in the Río Sabinas at least as far up as Storms' Ranch. This species is a predator on fishes and larger invertebrates, and its food habits on the northern Gulf coast have recently been discussed by Darnell (1958). Stations: 8A, 8B, 9A. Museum No.: TU 5646. Lepisosteus spatula (Lacépede). Alligator gar, "Catán" Atractosteus lucius Duméril. Duméril ( 1870, Tampico) Lepisosteus tristoechus (Bloch and Snyder). }ordan and Snyder ( 1901, Tampico) Lepidosteus tristoechus (Bloch and Snyder). Mcek ( 1904, Tampico) Streams of southeastern United States draining into the Gulf of Mexico and coastal lagoons south to Tampico, Vera Cruz, Mexico. Meek ( 1904) indicated the presence of the alligator gar in the markets where it is sold for food, and he mentioned that this fish is reported to be quite abundant in the large river channels and lagoons about Tampico. No specimens of the alligator gar were taken in the present study. In southern Texas Gunter ( 1945) captured the alligator gar in waters of nearly ma· rine salinity, although he stated that the species probably prefers waters of low sa­ linity. Natives of the headwaters are familiar with the species, calling it the "catán", but they indicated that this fish does not normally enter the shallow headwater streams. Food habits of the alligator gar on the northern Gulf coast have recently been dis· cussed by Darnell (1958). Station: 9A. ENGRAULIDAE-Anchovy F amily Anchoa hepsetus (Linnaeus). Striped anchovy Anchovia brownii (Gmelin). Jordan and Dickerson (1908, lagoon at Tampico) Along the Atlantic coast from Nova Scotia to Uruguay; also in the West lndies. The presence of the striped anchovy in the Tampico lagoons is highly likely, since it has been reported from bays and estuaries both above and below the Tampico area (see, for example, Hubbs, 1936; Gunter, 1945; Hoese, 1958). This anchovy feeds on small crustaceans, mainly copepods, and small bottom animals (Hildebrand and Schroeder, 1928; Hildebrand and Cable, 1930). On the North Carolina coast it ap· parently begins spawning slightly earlier than does A. mitchilli (Hildebrand and Cable, 1930). Station: 9A. Anchoa mitchilli (Valenciennes). Bay anchovy Anchovia mitchilli (Cuvier and Valenciennes). Jordan and Dickerson (1908, lagoon near Río Pánuco) Bays and lagoons of eastern North America from Maine to Yucatán. In the present study a single specimen was taken from the Laguna de Chairel, con· firming the presence of the hay anchovy in the Tampico area, and indicating its pene· tration of the fresher lagoons. As pointed out by Gunter ( 1945) the hay anchovy is euryhaline, and, although it has been reported to enter streams, it is normally en· countered in brackish to marine waters. Food studies of northern Gulf populations were reported by Darnell (1958). Stations: 9A, B. Museum No.: TU 5635. CLUPEIDAE-Herring Family Dorosoma cepedianum (LeSueur). Gizzard shad Dorosoma exile Jordan and Gilbert. Meek (1904, San Juan, Valles, Forlón) Dorosoma cepedianum (LeSueur). Jordan and Dickerson ( 1908, lagoon near Tam· pico) Eastern United States; coastal streams and lagoons from Massachusetts south to the Río Pánuco. In the present study 35 specimens of this fish were obtained from the Río Boquilla and its tributaries in the headwaters of the Tamesí, and 38 specimens were seined from the Laguna de Chairel at Tampico. The headwater specimens were taken from an ar­royo, a small lake, and from pools of the Río Boquilla from two to six feet in depth. No specimens were obtained from other headwater streams or from the Río Guayalejo at Adjuntas where the current was modera te to swift. Future collecting will probably reveal that this species is found throughout the fresh and brackish waters of the Tamesí drainage in pool and lake-like environments which are characterized by sorne turbidity, !ittle or no current, and mud or silt bottoms. 1t is known to be a resident of brackish waters on the northern Gulf coast. As pointed out by Hubbs, Ki..ehne, and Ball ( 1953) the gizzard shad is not readily taken in small seines, hence the species may be more widely distributed in the headwaters of the Tamesí than presently indicated. Food habits of the gizzard shad on the northern Gulf coast have recently been sum­marized by Darnell (1958) . Stomachs of five specimens from the Río Boquilla were examined, and ali were found to contain great quantities of finely-powdered silt. Sev· eral of the individuals had consumed large numbers of minute eggs of undetermined originas well as occasional specimens of Dilflugia sp. Stations: 6B, 6D, 6E, 8A, 9B. Museum Nos.: CNHM 4481, 62642; TU 5614, 5621, 5645. Dorosoma petenense (Günther) . Threadfin shad Signalosa mexicana ( Günther) . Meek (1904, V ali es) Gulf of Mexico and coastal lagoons from Florida west through Texas and south to British Honduras. In the present study 57 specimens were taken from the Laguna de Chairel at Tampico, but the species did not appear in any of the other collections from the Tamesí drain­age. The presence of this shad in Meek's collection from Valles, many miles from the Gulf, suggests that it may also be present in the larger streams and possibly in the headwaters of the Río Tamesí, even though it has not yet been collected there. Like the gizzard shad this species is not readily taken in small seines. The threadfin shad is known to have wide tolerance for salinity, and Gunter (1956) considered the species to be anadromous. On the basis of limited published information, the threadfin shad is considered to be a plankton feeder, although sorne bottom feeding may also take place (Darnell, 1958) . The taxonomic position of the threadfin shad has recently been discussed by Bailey et al (1954). Station: 9B. Museum No.: TU 5642. CH ARACIDAE-Characin F amily Astyanax fasciatus ( Cuvier) . Banded tetra Tetragorwpterus mexicanus Filippi. Jordan and Snyder (1901, Rio Axtla), Meek (1904, Forlón, Valles, Rascón) Tetragonopterus argentatus (Baird and Girard). Jordan and Snyder (1901, Río Verde) Astyanax argentatus Baird and Girard. Jordan and Dickerson (1908, lagoon near Tampico) Astyanax fasciatus (Cuvier). Miller (1956, La Media Luna) Coastal streams from southern and western Texas to South America. In the present study 2,025 specimens were obtained, and this fish was present in every collection made from the Ríos Sabinas, Frío, Boquilla, Mante, and Guayalejo. lt was also represented in every seine collection from the Arroyo Encino except those from the very shallow springs and spring creek. Surprisingly, the species was not obtained from the Laguna de Chairel at Tampico. The banded tetra is widely distributed throughout the headwater tributaries of the Río Tamesí system. It is probably found in the larger river, and the collections of Jordan and Dickerson (1908) demonstrate that this fish is also present in sorne of the coastal lagoons. The banded tetra is one of the most abundant species of fish in the headwaters of the Tamesí. Although it was found to be present in almost every available habitat type, the species was generally not abundant in very swift water, very shallow creeks, or lake-like areas. lt is primarily an inhabitant of deep river pools and moderately shal­low backwaters with sorne current. In the deeper clear, slow-flowing pools of the Río Sabinas around Storms' Ranch this species was very abundant, and it was frequently observed swimming at any depth (clown to 3 m), either singly or in tight schools of fifty or more individuals. These fish quickly investigated any disturbance of the water surface. At night this characin remained quiet in the deeper pools. The habitat of the banded tetra overlapped that of C. cyanoguttatum, and the two species were often ob­served together in mixed schools. Due to the wariness of the latter species, however, the seining data do not adequately reflect the association of the two species. Stomach contents of twenty·one individuals were examined, and the food of this characin was found to be quite variable. Vegetation made up 62 per cent of the food, animal matter made up 22 per cent, and detritus constituted the remainder. Most of the vegetation was filamentous algae (Spirogyra, Rhizodonium, Oscillatoria, and Hyalotheca) , although sorne fungus and green leaf fragments also were present. The filamentous algae were consumed in parallel sheaves which were clipped in bunches and tamped at the ends like elongated shredded wheat biscuits. Each "biscuit" was around five millimeters in length and contained about 55 strands of algae. About fifty such "biscuits" were required to fil! the stomach of a single fish. Most of the animal matter consisted of aquatic insects ( Coleoptera, Díptera, Homoptera, Odonata, and Trichoptera), as well as sorne of terrestrial origin, and one fish contained at least twenty different insects. Fish eggs and fish larvae were found in the stomachs of two individuals, one of which had consumed a total of twenty-four fish eggs. This little fish has wide food tolerances, and the frequency of utilization of each type of food is probably related to the availability of the food in the particular habitat. Meek (1904) suggested that spawning takes place in the latter part of May and early June. Information obtained by the present writer, however, indicates that in the Río Sabinas spawning probably begins no earlier than mid-June. Although females col· lected in April possessed mature eggs, on June 7th thousands of adult characins were observed schooling in an area of about twenty square meters at the head of naviga· tion where the Arroyo La Flor enters the Nacimiento. These fishes were not spawning, but they apparently were awaiting rains to afford them passage further up the Arroyo La Flor where spawning must occur. The ripe ovary of a moderate-sized adult female contained about 1,500 eggs of small size (ca. 0.8 mm in diameter) . Stations: lF-H, J-L; 2A; 3A-E; 4A-L; 5A; 6A-E; 7A-D; 8A, B. Museum Nos.: CNHM 4480, 62643, 62652, 62664, 62672; TU 5569, 5583, 5590, 5591,5599,5606,5608,5616,5622,5628,5657,5666,5670,5685,5690. CATOSTOMIDAE-Sucker Family lchtiobus bubalus (Rafinesque). Smallmouth buffalo, "Boquin" Carpiodes tumidus Baird and Girard. Jordan and Snyder (1901, Tampico Lagoons) Meek (1904, Forlón) lctiobus tumidus (Baird and Girard). Regan (1908) lctiobus bubalus (Rafinesque). Hubbs (1930) Larger rivers and lakes from Canada and eastern United States south to the Río Tamesí. During the present study no suckers were captured although they were frequently observed. One large sucker was often seen in the depths of the Nacimiento of the Río Sabinas. On severa! occasions in late May· a group of suckers was observed in the Río Sabinas a few hundred meters above Storms' Ranch where they congregate, appar· ently awaiting higher water from the spring rains for upstream passage of shallow riffies. Two large specimens which had been speared from this group by the natives were examined briefly by the writer after they had been partially prepared for cooking. These specimens were identifiable to genus but not to species. Both were ripe females. Another sucker, lctiobus labiosus (Meek), has been recorded from the drainage of the Río Pánuco, and this species may also be present in the Río Tamesí. Stations: 8A, 9A. Museum No.: CNHM 4476. CYPRINIDAE-Minnow Family Dioruia rasconis (Jordan and Snyder). Notropis rasconis Jordan and Snyder. Jordan and Snyder (1901, Rio Verde, Rascón) H ybognathus ;asco nis (Jordan and Snyder) . Meek ( 1904, Río Pánuco) Dioruia rasconis (Jordan and Snyder). Miller (1956, Río Verde, La Media Luna) Endemic to the Pánuco-Tamesí drainage system. In the present study 1,904 specimens were taken. This fish was found to be abundant in collections from the Arroyo Encino and the Ríos Sabinas, Boquilla, and Guayalejo. lt was entirely absent from the Río Mante collection, being partially replaced by Dioruia sp., and it was not obtained from the Laguna de Chairel at Tampico. This minnow is widespread and abundant in most headwater tributaries of the Tamesí system, and it may be present in the larger rivers, as well. Moore (1957) put forth reasons for separating Dioruia from Hybognathus, and Clark Hubbs and Brown (1956) discussed the status and relationships of the three described species of the genus Dionda. D. rasconis inhabits shallow backwater and pool areas and is often associated with weed beds. lt was abundant in many areas of the Río Sabinas at the edge of the main current, but it appeared equally' successful in isolated pools of the arroyos and the Río Boquilla without current. This species also frequented shallow gravel rifHes where the current was slow. Mud or silt bottoms appeared to be important, and the absence of suitable bottoms may have been responsible for the apparent absence of this fish from the uppermost reaches of the Arroyo Encino, Nacimiento of the Río Sabinas, the Río Frío, the spring pool of the Río Boquilla, and the Río Mante. The stomachs of 20 specimens were examined and all contained food. Arthropod remains (insects and water mites) made up about one-fifth of the stomach contents. Bits of filamentous algae and occasional diatoms made up about one-tenth, and the remaining material was bottom detritus and such matter as would be consumed with the detritus. It is obvious that this minnow feeds primarily upon detritus gleaned from the surface of the bottom. In the process it also ingests sand grains, bottom diatoms (Navícula, Pinnularia, Sirurella, etc.), scraps of filamentous algae (Aphanizomenon, Lyngbya, Rhizoclonium), desmids (Micrasterias), and bits of fungi and vascular plant matter. The presence of numerous small arthropods suggests sorne selectivity in feeding. This minnow is one of the severa} species which nip at bathers in the river. Great numbers of young were attracted to the turbid water created by roiling the boUom of a.clear area with window screening (Station 4H). Males of this species taken on the 2lst of December from grave! riffies of the lower Arroyo Encino exhibited breeding tubercles, and spawning may have been in progress at the time of capture. Stations: lG, H, J-L; 2A; 3A-C; 4B, D-L; 6B-E; 8A, B. Museum Nos.: CNHM 4477, 62644, 62654, 62674; TU 5573, 5579, 5589, 5595, 5605,5609,5615,5627,5648,5683,5688. Dionda sp. Known only from the Río Tamesí. In the present study 197 specimens of this undescribed minnow were taken from the headwaters of the Río Tamesí. The species appeared in collections from the lower two-thirds of the Río Sabinas, the Nacimiento of the Río Frío, the Río Mante and the Río Guayalejo at Adjuntas. This fish is primarily an inhabitant of clear waters which show a fair current, and to sorne extent it replaces D. rasconis in such habitats. The two species were frequently· taken together, however. This minnow was seldom taken in large numbers except in the clear, slow, weedy waters of the Río Frío near its Nacimiento. In the clear flowing irrigation ditch of the Río Mante this species was easily recognized, and large numbers were observed together with A. fasciatus and G. vittata feeding upon the filamentous algae and other organic matter which could be gleaned from the surface of a concrete culvert. Because of the depth and current the seine collection (7A) does not fairly represent the abundance of Dionda sp. at this location. This handsome minnow is notable in possessing a dark, well-defined, unbroken lateral band characteristic of certain fishes which inhabit clear flowing streams. The association of this minnow with Gambusia vittata is discussed later. Males of this minnow taken on the 2lst of December from gravel riffies of the lower Arroyo Encino exhibited well-developed breeding tubercles, and spawning may have been in progress at the time of capture. Although both species of Dionda apparently spawn in riffies at about the same time, field data suggest that the breed­ing aggregations tend to occupy slightly different habitats, either different riffies or different areas of the same riffies. Stations: lJ-L; 4D-F,K,L; 5A; 7A,D; 8B. Museum Nos.: CNHM 62653, 62665, 62673; TU 5571, 5580, 5649, 5668, 5678. Notropis lutrensis (Baird and Girard). Red shiner Nototropis forlonensis Meek. Meek (1904, Valles, Forlón) Cyprinella forwnensis (Meek). Jordan, Evermann, and Clark (1930) Notropis lutrensis forlonensis Meek. Hubbs (1954) Originally distributed from South Dakota, Minnesota, and Illinois southward and and westward through Texas into northern Mexico; in Gulf coastal streams as far south as the Río Pánuco system. In the present study 70 specimens were obtained from the lower two-thirds of the Río Sabinas and from the Río Guayalejo at Adjuntas. lt was not encountered in the Ríos Frío, Boquilla, or Mante or in the Laguna de Chairel. In the Río Sabinas this minnow was taken only in the deeper pool areas with or without current. It appears to be primarily an inhabitant of the larger downstream waters, and future collecting should reveal this species in larger waters of the Río Tamesí itself. Examination of the stomach contents of five individuals revealed over 20 insects, one water mite, six large protozoa, and sorne filamentous algae and detritus. These minnows appeared to have been feeding rather selectively upon insects, and the algae and detritus were probably incidental. Meek ( 1904) stated that the spawning time is the latter part of May. This was not verified by the specimens examined in the present study since the ovaries of all fe. males appeared to be immature. Sorne of the males, however, appeared to be develop· ing breeding tubercles which might suggest a late spring (June) spawning. Stations: 4H,J-L; 8A,B. Museum Nos.: CNHM 4478, 4479, 62656, 62676; TU 5654, 5682. Notropis sp. Known only from the Río Tamesí. In the present study 144 specimens of this undescribed minnow were taken from the headwaters of the Río Tamesí. Specimens were obtained from the middle and lower stretches of the Río Sabinas and the Río Guayalejo at Adjuntas. It was not found in the Ríos Frío, Boquilla, or Mante or in the Laguna de Chairel. The distribu­tion of this minnow appears to be somewhat similar to that of N. lutrensis. The abundance of the present species in the Río Guayalejo and in certain backwater areas around Storms' Ranch, however, suggests that, whereas this fish does inhabit the larger rivers, it is also at home in shallow upstream backwaters such as the mouth of the Arroyo Encino. During the course of the field work numerous observations were recorded of small cyprinid fishes swimming in loose schools at the surface of deep (2-3 m) clear water in the Río Sabinas around Storms' Ranch. These minnows often nibbled at the organic .material present on tree roots at the edge of the deep water and were immediately attracted to any minor surface disturbance, such as an insect falling into the water. The individuals would scatter at any major disturbance but would return shortly to continue their surface activity. Although the identification is not positive, these observations apparently relate to the present species. Specimens of this small surface minnow could be captured selectively by a small-meshed net lowered below the sur­face of the water and quickly raised after the fish had returned. Stations: lK, L: 4D, F, 1, K, L; 8B. Museum Nos.: CNHM 62655, 62675; TU 5572, 5578, 5655, 5681. ARIIDAE-Sea Catfish Family Galeichthys felis (Linnaeus). Sea catfish Galeichthys güntheri Regan. Jordan and Dickerson ( 1908, Tampico) Galeichthys felis (Linnaeus) . Hubbs (1936) Along Atlantic coast of North America from Cape Cod to Florida, and along Gulf coast at least as far south as Vera Cruz and Yucatán, Mexico. The sea catfish is one of the most abundant species inhabiting the estuaries of the northern Gulf coast, and it has been reported from the mouths of tropical rivers sorne distance from the Gulf in southern and eastern Mexico by Hubbs (1936). lts presence in the Tampico lagoons is anticipated. Food habits of the sea catfish on the northern Gulf coast h:ave been studied by Gunter (1945), Darnell (1958), and others, and the spawning season in southern Texas has been discussed by Gunter (1945, 1947). Station: 9A. lcTALURIDAE-Catfish Family lctalurus australis (Meek). "Bagre" Amiurus australis Meek. Meek (1904, Forlón) lchthyaelurus punctatus (Rafinesque) . Meek (1904) Streams entering the Gulf in east-central Mexico from the Río Tamesí south to the Río Blanco in southern Vera Cruz. This fish is a close relative of l. punctatus, but, according to Car! Hubbs (personal correspondence), it constitutes a distinct species. In the present study 56 specimens of this catfish have been taken from the upper and middle stretches of the Río Sabinas, from the Boquilla and from the Guayalejo at Adjuntas. Young individuals were taken by seine in the muddy waters of the Río Boquilla and Río Guayalejo. Adults are not as readily taken by seine, particularly in the daytime. Observations as well as captures with hooks and fyke nets indicated that this species is abundant in the Río Sabinas as far up as the Nacimiento, and a single adult specirnen was obtained frorn a rocky pond in the Arroyo La Flor above the Nacimiento. The species is undoubtedly of widespread distribution within the drain­age in both clear and turbid waters of the tributaries and larger rivers, as well. In the clear waters around Storms' Ranch l. australis was frequently observed, and the observations were verified by specimens. This catfish resides during the day in caves and crevices under the banks, especially where they are undercut by the current or where roots of cypress trees forrn extensive caverns under the banks. These shelters are shared during the daytirne with the giant tropical freshwater shrimp, Macrobrachium carcinus, and they provide temporary haven for large cichlids, C. cyanoguttatum, when the latter are disturbed. The catfishes may be drawn out of the crevices and even captured on a hook in the daytirne by the strong odor of decaying flesh ( rotten beef liver is most eff ective). They norrnally remain hidden during the day, however, and become active at dusk. At first one or two will venture a short way frorn the shelter, swirn around for a moment, then return. This procedure continues with increasing numbers until the entire local school has become active. These then approach the center of the stream, form a column, and proceed roughly in single file clown to the neighboring pool for night-time foraging. In such columns the largest individual is foremost, and subsequent individuals are ranked in approximate order of size with the smallest seemingly playing an irresponsible game of tag at the rear of the column. At night they are readily taken in the pools by trot lines, hand lines, or fyke nets. Stomach contents of six individuals were examined, and ali contained much food material. Two small specimens from the Río Boquilla had fed directly upon bottom material and contained much detritus and many insect larvae (mostly Díptera, but including sorne Ephemeroptera and Odonata) . Larger individuals from the Río Sabinas had consumed a wide variety of food items of plant and animal origin. Plant material included fruit of the strangling fig tree (Ficus segoviae), and various seeds, buds, and bits of leaves. Animal material included aquatic insects, exoskeleton of the tropical river shrimp, Macrobrachium carcinus, and remains of cichlid fishes. Sorne detritus and undetermined organic matter were also present. Food habits of this species appear to be quite similar to those of the closely related channel catfish (Darnell, 1958). Gonads of all specimens appeared to be immature in the spring. Stations: IN; 3C; 4D,E,G; 6B-D; 8A,B. Museum Nos.: CNHM 4474, 4475, 62646, 62688; TU 5594, 5611, 5625, 5660, 5693. lctalurus furcatus (LeSueur). Blue catfish, "Bagre," "Pintontle" lctalurus furcatus (LeSueur). Jordan and Snyder (1901, Tampico), Jordan and Dickerson ( 1908, Tampico) lchthyaelurus furcatus (LeSueur). Meek (1904) Principally in large rivers from the Mississippi River valley west and south to the Pánuco-Tamesí drainage. This catfish, which has been recorded in the Río Tamesí system as/. furcatus and which is clearly a southern representative of this group, may be sufficiently divergent to warrant its eventual separation as a distinct species (Car! Hubbs, personal cor­respondence). In the present study 19 specimens were taken in two collections from deep pools in the Ríos Boquilla and Guayalejo. Although the blue catfish is not readily taken in small seines, its absence from upstream collections by various types of gear suggests that the species inhabits the larger, more turbid waters, and it is probably abundant in the Río Tamesí proper. This species may occasionally enter the head­waters, and a large catfish captured severa! years ago at Storms' Ranch which was said to have weighed about twenty-five pounds probably belonged to this species. The blue catfish may also be present in the deeper portions of the Ríos Mante and Frío, and since the species is known to be a frequent invader of brackish-water areas (Gunter, 1945; Darnell, 1958), it might be expected to occur in the lagoons around Tampico. Food habits of the blue catfish on the northern Gulf coast have been discussed by Darnell (1958). In the present study the stomach contents of five small specimens from the Río Boquilla were examined. These contained a great many immature and adult insects ( chiefly dipteran larvae, but also including Coleoptera, Ephemeroptera, Fishes of the Río Tamesí and Hymenoptera). Other material included eggs (probably fish roe), halls of algae, and bits of undetermined organic matter and detritus. Food of adult blue catfish in the Tamesí area has not been studied. Stations: 6D, 8B, 9A. M useum Nos. : CNHM 62645; TU 5659. lctalurus mexicanus (Meek). Amiurus mexicanus Meek. Meek (1904, Rascón, Río Verde) lctalurus mexicanus (Meek). Miller (1956, Río Pánuco) Known only from the Pánuco-Tamesí system. This little catfish is closely related to /. lupus of the streams farther north, but according to Carl Hubbs (personal correspondence) the Pánuco-Tamesí form rep­resents a distinct species. The material reported here represents the first record of its occurrence in the Río Tamesí. In the present study three specimens were obtained in a single collection from the Río Guayalejo at Adjuntas. The same collection con­tained specimens of both the other known species of the genus and permitted the first clear analysis of the I ctalurus complex from this drainage, establishing the validity and relationships of / . mexU:anus. Since this species appeared only in the single collection, its intradrainage distribution is not understood. l. lupus has been considered by Hubbs, Kuehne, and Ball (1953) and others ~o be an inhabitant of springs and other headwaters in the Texas stre'ams. The same may be true of the southern representative, /. mexicanus, but at present there is no evidence to support this concept. Station: 8B. Museum No.: TU 5653. SYNGNATHIDAE-Pipefish Family Oostethus lineatus (Kaup) . Opossum pipefish Doryrhamphus lineatus (Valenciennes). Jordan and Dickerson (1908, Tampico lagoons) Oostethus lineatus (Kaup). Hubbs ( 1929) Both sides of the Atlantic and in the New World from South Carolina to Brazil; also found in Cuba anda number of the West lndian islands. No pipefishes were taken during the present study. Herald ( 1942) pointed out that a number of nominal species are probably synonyms of O. lineatus, and he also modified the known geographic range of tbe species. Hubbs (1929) noted that this pipefish is chiefly an inhabitant of brackish waters, but that it ranges into purely fresh water and doubtless also in to the sea. Hildebrand ( 1939), however, indicated that this fish is quite at home in the fresh waters of Panama, and he took males bear­ing eggs from Gatun Lake, showing that the fish breeds in the lake and that it is probably a permanent resident there. Station: 9A. CYPRINODONTIDAE-Killifish Family Cyprinodon variegatus Lacépede. Sheepshead minnow Cyprinodon elegans Baird and Girard. Jordan and Snyder (1901, lagoons near Tam­pico) Coastal lagoons from Maine to South America and throughout the W est lndies. C. elegans is now considered to be restricted to certain localities in Texas (Miller, 1951), and C. variegatus, which is known to extend at least as far south as the tip of Yucatán (Miller, 1955), is the only representative of this genus whose presence in the lagoons around the mouth of the Río Tamesí would be anticipated. No speci­mens of any Cyprirwdon were obtained in the Laguna de Chairel collections, and the presencc of this estuarine species in the drainage needs verification. Station: 9A. Fundulus grandis Baird and Girard. Gulf killifish Fundulus heteroclitus (Linnaeus). Jordan and Snyder (1901, lagoons near Tampico) Fundulus grandis Baird and Girard. Miller (1955) Brackish waters from northeastern Florida westward along the northern Gulf coast and south along the Mexican coast at least to Laguna de Tamiahua, south of Tampico; also on north coast of Cuba. Miller (1955) has shown that F. heteroclitus is restricted on the Gulf coast to the state of Florida, and he has further indicated that F. grandis extends south along the Mexican coast past Tampico. Regarding its habitat, Miller (1955) has pointed out that the species is found typically in brackish water, less commonly entering foil sea water, and penetrating fresh water in the southern part of its range. No specimens of the gulf killifish were obtained in the Laguna de Chairel collections, and the presence of this species in the drainage, although highly probable, is in need oí verification. Station: 9A. Fundulus simüis (Baird and Girard) . Longnose killifish Fundulus similis (Baird and Girard). Miller (1955, north of Tampico) Brackish water from northeastern Florida along the northern Gulf coast and south­ward into Mexico at least as far as a lagoon 35 miles north of Tampico. The longnose killifish has never been recorded from the Río Tamesí drainage, and it is listed here on the hasis of Miller's (1955) record from a lagoon 35 miles north of Tampico. The species is known to enter nearly fresh water (Gunter, 1945, 1950; Reid, 1954), and, although it is anticipated, its presence in the drainage should be verified. lucania parva (Baird and Girard). Rainwater killifish Lucania venusta Girard. Meek ( 1904, lagoons north of Tampico) Coastal swamps of the eastem United States from Massachusetts south and west across the Gulf coast to Texas and New Mexico, then south to Tampico, Mexico. Two specimens taken from the Laguna de Chairel in the present study represent the first record of this species from the Tamesí drainage. Since the rainwater killi­fish is known to enter fresh water in the southern part of its range, this species may be distributed rather widely in the low-lying coastal marshes of the Tamesí drainage area. Station: 9B. Museum No.: TU 5634. PoECILIIDAE-Livebearer Family Gambusia affinis (Baird and Girard). Mosquitofish Gambusia affinis (Baird and Girard). Jordan and Snyder (1901, Tampico lagoons), Meek (1904, Rascón, Valles, Forlón), Regan {1913, Tampico) Originally native from Alahama and southern Illinois south and west through Texas and south along the Mexican coast to the Pánuco-Tamesí system. Early' workers did not distinguish between this and the severa! other gambusias which inhabit the drainage. Therefore, all records before Hubbs' (1926) study of the genus are doubtful. Hubbs (1926) reexamined Meek's specimens from Rascón, Valles, and Forlón, and from this material he described three new species, G. panuco, G. regani, and G. vittata. Hubbs (1926) made no mention, however, of G. affinis or of another (undescribed) species in the Pánuco-Tamesí complex. As pointed out by Bailey, et al. (1954), Gunter (1956), and others, G. affinis is a frequent invader of brackish water. In the present study 107 specimens of G. affinis were obtained in collections from the Río Mante and from the Laguna de Chairel at Tampico. lts presence in these col­lections and its absence from others suggest that in the Tamesí area the species prefers lake-like conditions with ample vegetation and virtually no current. This species was never collected with either G. panuco or G. regani, which occupy some­what similar habitats in the other tributaries. Each of the three species appears to have become better adapted than the other two to life in a particular headwater stream. The mutually exclusive distributions of these three very similar and closely related species suggest competitive elimination of ecologically equivalent species. G. affinis was taken together with G. vittata and Gambusia sp. As mentioned below the habits of G. vittata are quite different and, indeed, unusual for a gambusia, implying little competition with the other gambusias. Not enough is known about the hahitat of the new species of Gambusia to comment on relations with its congeners. Analysis of the stomach contents of three individuals revealed three adult insects, two water mites, and little else. Simpson and Gunter (1956) reported that two speci­mens from the coastal waters of Texas contained small fish, small crustaceans, and annelids. This gambusia is widely recognized as a voracious predator on small arthropods, consuming both aquatic forros and non-aquatic insects which fall to the surface of the water. · Krumholz (1948) has considered in detail the reproductive habits of this species in Illinois. Stations: 7B-D; 8A (?); 9A (?),B. Museum Nos.: CNHM 62666; TU 5637, 5673. Gambusia panuco Hubbs. Gambusia affinis (Baird and Girard). Meek (1904, Rascón, Valles) (in part) Gambusia panuco Hubbs. Hubbs ( 1926) Known only from the Pánuco-Tamesí drainage sy'stem. In the present study 209 specimens were obtained in five collections from the Río Boquilla thereby extending the known range of the species to the Río Tamesí system. This gambusia which appeared to be widespread in the Boquilla was not encountered elsewhere in the drainage, nor was any other species of gambusia taken in the Río Boquilla, not even the wide-ranging and ecologically divergent G. vittata with which it apparently did occur in Meek's Valles collection. Within the Río Boquilla drainage G. panuco seemed to prefer the smaller, less turbid waters, but it was also fairly abundant in the deeper arroyo and the very turbid pools of the Río Boquilla proper. lt was least frequent in the lake. On the basis of its wide habitat tolerances, this species would certainly have been expected to occur in the Río Sabinas and, perhaps, in the Ríos Frío and Mante. Unfortunately, the stomach contents of only two specimens were examined. To· gether these contained two insects, four water mites, one cladoceran, one rotifer, and numerous arthropod egg cases. This fish apparently subsists upon small arthropods and zooplankters. One large female collected in early April contained 17 well-de­veloped young. Stations: 6A-E. Museum Nos: CNHM 62647; TU 5610, 5619, 5623, 5632. Cambusia regani Hubbs. Cambusia affinis (Baird and Girard). Meek ( 1904, Forlón) (in part) Cambusia regani Hubbs. Hubbs (1926) Known only from the headwaters of the Río Tamesí. Hubbs (1926) suggested that G. regani probably also occurs in the Río Soto La Marina which enters the Gulf north of the Tamesí, but this has not been confirmed. In the present study 171 specimens were obtained from the Río Sabinas and its tribu­tary arroyos, and a single questionable specimen appeared in the Río Guayalejo col­lection near the mouth of the Río Sabinas. G. regani is a fish of small pools and shal­low, weedy backwaters, and it was seldom found in water with more than a very slight current. lts center of population density appeared to be the Arroyo Encino where it was taken in almost every arroyo seine collection from the springs above Encino down to the junction with the Río Sabinas. lt also appeared in ponds above the Nacimiento and in backwaters throughout the length of the Río Sabinas. This fish was never found in large concentrations. Stomach contents of 20 specimens were examined of which 18 contained food. Larval and adult insects made up 85 per cent of this material. About half of these in­sects were chironomid larvae, but the larvae of Coleoptera and Trichoptera and adults of Coleoptera, Diptera, and Hymenoptera also were present. Additional animal remains included a well-digested snail, a water mite, and arthropod eggs. A few strands of filamentous algae and a small amount of detritus made up the remainder. Over 95 per cent of the material encountered was of animal origin, and it is clear that this highly predaceous little fish subsists almost entirely upon small arthropods with emphasis upon chironomid larvae. Seven females taken in late April and early May all contained young. Six females 23-27 mm in length averaged 5.8 embryos per female, whereas the single large female (32 mm) contained 13 mature young. Stations: lB-E,G,H,J-L; 2A; 3C,D; 4A,B F,G,J-L; 8B (?). Museum Nos.: CNHM 14033-45, 62657, 62678; TU 5568, 5575, 5588, 5596, 5658(?)' 5679. Cambusia vittata Hubbs. Cambusia affinis (Baird and Girard) . Meek ( 1904, Valles) (in part) Gambusia vittata Hubbs. Hubbs ( 1926) Known only from the Pánuco-Tamesí drainage system. In the present study 1,139 specimens were taken from the headwaters of the Río Tamesí. This gambusia was obtained from the middle and lower stretches of the Río Sabinas, the Ríos Frío and Mante, and the Río Guayalejo at Adjuntas. The distribu­ tion of this fish closel y parallels that of Dionda sp. Both species were absent from the Arroyo Encino except near the Río Sabinas. Both were absent from collections made in pools of the Arroyo La Flor, the Nacimiento, and upper reaches of the Río Sabinas, the Río Boquilla, and the Laguna de Chairel. Unlike Dionda sp., however, G. vittata was generally° present in large numbers in suitable environments of the Río Sabinas, and the habitat relations of this species can be stated with greater certainty. This gambusia inhabits clear waters with slow to moderate current. lt was -0ften abundant in weedy backwaters and areas of dense algal growth. In the Sabinas and lower pools of the Arroyo Encino this species was often present with G. regani, but the two species were never abundant together. In the Río Mante G. vittata was present in several collections with G. affinis, and these two were obtained together with Gambusia sp. in a single collection. G. vittata was not present in the Río Boquilla with G. panuco, but they both apparently occurred together in Meek's collection from the Río Pánuco (Valles). From the available evidence it appears that G. vittata is notan important ecological competitor with any of the other species of Gambusia. lt tends to inhabit clearer and swifter waters than any of the other species, and, as pointed out below, its food habits are remarkable for a member of this genus. This gambusia parallels Dionda sp. in the possession of a dark, well-defined, unbroken lateral band. Stomach contents of 20 specimens were examined, of which eighteen contained food. Fifty per cent of the material encountered was filamentous algae (mostly Spiro· gyra with sorne Rhizoclonium). This fish exhibits the unusual ability to swallow Spirogyra in neat sheaves with the strands parallel, rather than in halls or tangled networks as a number of other small fishes do. Arthropods made up only 20 per cent of the stomach contents and included the remains of insects, water mites, and arthro· pod eggs. Protozoa (ArceUa) constituted one per cent, and undetermined organic matter and detritus made up the remainder. The habit of consuming large amounts of algae and detritus is not at all typical for fishes of the genus Gambusia, and they seem to be primitive characters rather than recent specializations within the genus. If these stomach contents are truly representative, this fish does not closely compete for food with any other gambusiin fish examined. As mentioned below an interesting relation apparently exists between feeding habits and reproductive habits. Of the nine females examined from April collections, only one failed to contain developing young. Females 25-30 mm averaged 9.5 young per pregnant female, whereas the single 31 mm female possessed 14 developing embryos. In most collec· tions the sex ratio was about even, but one backwater collection ( 4D) contained 45 females and a single male and appeared to have taken females "in labor." This col· lection was made in water a few centimeters in depth with many Spirogyra mats ftoating on the surface and clinging to the rocks. Three females with mature eggs had eaten well. Three females with large young (including one which had apparently already delivered several young) had fed very little. One female which had obviously recently delivered her brood was stuffed with food. All females with mature young and the recently delivered female had consumed only algae, but the others also in· cluded arthropods. If the situation is interpreted correctly, it appears that this fish, which normally remains close to the current, enters the very shallow, algae-laden backwaters largely for delivery of the young. As the young near full term the female undergoes a period of fasting. After the young are born the female feeds heavily, but, to avoid the danger of consuming her own young, she becomes largely a vege­tarian during this period. For this reason the algae-eating habits of this species may be somewhat exaggerated, but it is quite remarkable that they consume algae at ali. Stations: lJ-L; 4D-F, H-L; 5A; 7A-D; 8A,B. Museum Nos.: CNHM 14046-58, 62658, 62668, 62677; TU 5570, 5576, 5656, 5665, 5671, 5676. Gambusia sp. Known only from the Río Tamesí drainage. Seven specimens of this undescribed species of Gambusia were obtained in a single collection from the reservoir of the Río Mante. Judging from its occurrence in the reservoir collection this species probably inhabits weedy margins of lake-like areas. Nothing is known regarding its food or breeding habits. According to Hubbs (per­sonal correspondence) this is not the species which Ahl ( 1923) described from "habitat Mexico" as G. modesta and later (1925) changed to G. myersi because of preoccupation of the former name. Station: 7D. Museum No.: CNHM 62667. Mollienesia formosa (Girard). Amazon molly Mollienisia formosa (Girard). Regan (1913, Tampico) (incorrectly), Hubbs and Hubbs (1932) Streams from southwestern Texas south to the Río Tamesí. C. L. Hubbs (1926) suggested that Regan's material listed as M. formosa probably included specimens of M. latipinna and M. sphenops which were previously known from the drainage, and in 1933 Hubbs pointed out that this material was actually referable to M. latipinna. In 1932 C. L. Hubbs and L. C. Hubbs recorded live speci­mens which had been taken from Forlón in the Tamesí drainage for breeding pur­poses. In the present study a single specimen of the Amazon molly was collected from the Río Guayalejo at Adjuntas in the company of M. sphenops. Bailey and Miller (1950) have discussed the spelling of the generic name. Habitat relations and food habits of this species have not been studied within the drainage. Judging by its close association with the euryhaline M. latipinna, at least in the Texas portion of its range, this fish probably enters waters of low salinity, but confirmatory records seem to be lacking. The remarkable sexual condition and reproductive behavior of this species based upon extensive laboratory breeding experiments have been considered in a series of papers by C. L. Hubbs ( 1933, 1934, 1955) and by C. L. Hubbs and L. C. Hubbs ( 1932, 1946) . Meyer ( 1938) studied cytogenetic aspects of reproduction in the Amazon molly. Recently Clark Hubbs, Drewry, and Warburton (1959) described a single male specimen from southern Texas which they interpreted as being a male representative of M. formosa. Miller and Schultz ( 1959) , however, ha ve pointed out that the specimen might have been a hybrid between M. sphenops and M. latipinna. The latter authors also reported the all-female but non-gynogenetic condition in a related group of poeciliid fishes (Poeciliopsis) from northwestern Mexico. As noted by Hubbs and Hubbs (1932), in the headwaters of the Río Tamesí M. sphenops is undoubtedly the species with which M. formosa consorts. If the Amazon molly does frequent the coastal lagoons around Tampico, it probably enjoys intimate F ishes o f the Río T amesí association with males of both M. spherwps and M. latipinna. M. latiputictata, which is more distantly related, undoubtedly does not become involved. Station: 8A,B. Museum Nos.: CNHM 15592-16647; TU 5651. Mollienesia latipinna LeSueur. Sailfin molly Mollienisia latipinna LeSueur. Jordan and Snyder (1901, Tampico lagoons), Regan (1908, Tampico), Hubbs (1926, 1933) Mollíenisia formosa (Girard). Regan (1913) Coastal swamps from South Carolina across the northem Gulf and south along the Mexican coast to Campeche. As mentioned previously, Hubbs (1926, 1933) pointed out that specimens which Regan (1913) recorded from Tampico as M. formosa were, in reality, M. latipinna. The sailfin molly was not taken in the present study, not even in the large collection from the Laguna de Chairel. The species is known to enter freshwater, however, and further collecting will be necessary to establish details of its distribution in the lagoons about Tampico. Ecological relations of the sailfin molly on the Texas coast have been discussed by Gunter (1945, 1950) and by Simpson and Gunter (1956). Station: 9A. Mollienesia latipunctata (Meek). Poecilw latipunctata Meek. Meek (1904, Forlón) Mollienisia latipunctata (Meek). Hubbs (1933) Known only from the headwaters of the Río Tamesí. Hubbs ( 1933) pointed out that this species is limited to the Río Tamesí and its tributaries. In the present study 464 specimens were taken from the waters of the Río Mante, although the species did not appear in any of the other collections from the drainage. This molly was well represented in all of the Río Mante collections, but it was particularly abundant in the collection made at the Nacimiento (7C) where the water was deep, clear and flowing and contained extensive beds of submerged vegeta­tion. Since the Río Mante collections covered a wide range of habitat types, the ab­sence of this fish from collections in the other tributaries may have been due to biological rather than to physical factors. M. sphenops which was widely distributed throughout the headwaters of the Río Tamesí was present with M. latipunctata in all of the Río Mante collections. In the irrigation ditch and reservoir where M. latipuctata was abundant M. spherwps made up less than five per cent of the collections. Below the dam, however, where creek-like conditions prevailed, M. sphenops was more than twice as abundant as M. latipunctata. The spotted molly appears to be more at home in deep, clear waters, but future work will be required to clarify the observed distribu­tion patterns. lt should be pointed out that the lateral spots on M. latipunctata, particu­larly the females, form a dark, almost continuous lateral band effect somewhat similar to that observed in D. rasconis and C. vittata, which also tend to inhabit clear flowing waters. Stomach analyses were carried out on five specimens. These ali contained much mud and bottom ooze with which were mixed a few strands of green and blue green algae and sorne diatoms and sand grains. This species obviously feeds from the bottom, but the location, mechanics, and behavior of feeding are unknown. Meek (1904) mentioned that a specimen taken at Forlón in mid-May contained 16 developing young. In the present study four females collected in early }une were found to possess immature eggs, and at least one group had been fertilized. Hubbs ( 1933) indicated that in laboratory aquaria this species produces very small broods, and although the young are large at birth they develop very very slowly. Stations: 7A-D, 8A. Museum Nos.: CNHM 4484, 4485, 62669; TU 5672. Mollienesia sphenops (Valenciennes). Poecilia limantouri Jordan and Snyder. Jordan and Snyder (1901, Río Tamesí, Tam­pico, Rascón, Río Verde) Poeciliasphenops Cuvier and Valenciennes. Meek (1904, Forlón) Mollienisia sphenops (Cuvier und Valenciennes). Regan (1913), Hubbs ( 1933) Coastal streams from the Río Grande basin southward to northern South America. In the present study 2,949 specimens were taken from most collections made in the Ríos Sabinas, Frío, Boquilla, Mante, and Guayalejo. Although the species failed to appear in the Laguna de Chairel collection, the reference by Jordan and Snyder (loe. cit.) confirms its presence in the low coastal lagoons. This fish is known to enter brackish-water, and Gunter (1956) has considered it to be euryhaline. This molly is distributed widely throughout the shallow waters of both the Pánuco and the Tamesí, and, in the latter stream at least, it is one of the three most abundant species · (together with A. fasciatus and D. rasconis). This molly is a bottom inhabitant, and although it has wide habitat tolerances it seems to prefer small creeks where it utilizes both shallow pools and riffies. This fish shows a decided preference for rocky bottoms which are richly covered with a carpet of ooze containing sorne filamentous algae ( especially blue-greens) , diatoms, proto­zoans, and decaying bits of lea ves and other matter. Silt bottoms also are accepted, and, as indicated by its presence in the Río Boquilla collections, the species exhibits a wide tolerance for turbidity. This molly was most often found in circumstances where the current was slow or absent, and it was gen­erally not abundant in larger bodies of water or where the current was moderate to swift. During the spring, however, when torrential rains send rivers over their banks and connect roadside ditches with the creeks and arroyos, swarms of these adventurous little fish swim upstream and are seen to be active in small surface waters every­where throughout the countryside severa! miles from the nearest permanent water. Comparative habitat relations and possible ecological competition between this species and M. latipunctata have already been mentioned. Stomach analyses were carried out on eighteen specimens, of which seventeen con­tained food. Each stomach possessed much unidentifiable detritus and decaying or­ganic matter, as well as filamentous algae (Lyngbya, Oscillatoria, Spirogyra, Ulo­thrix, U ronema) , diatoms ( N avicula, Pinnularia, Sirurella) , desmids (Cosmarium, Pediastrum), and bits of vascular plant material. Sorne silt and sand also· were en­countered. Even though the fishes for stomach analyses were purposely selected from severa! different stations and environments, the stomach contents varied only slightly from one individual to another. This molly feeds from the exposed surfaces of rocks, stones, and other bottom features. lt apparently utilizes its broad, flat, tooth-covered lower lip as a brush or rasp to clean the algae and other accumulated living and non­ living matter fr.om such surfaces. Whereas little sorting of the rasped food seems to be involved, the fish obviously exhibits selectivity in determining the surfaces to be used for feeding. All eight of the females examined above forty mm in length which had been taken in April contained developing young. The number of young varied with the size of the female from 13 in the smallest to 35 in the largest, and one of the larger females contained 52 mature but unfertilized eggs. Brood sizes in aquarium-reared M. for­mosa, M. latipinna, and M. sphenops were given by Meyer (1938), who found the maximum number per female to be 105, 84, and 117, respectively. Krumholz (1948), however, reported a female Gambusia affinis with 315 developing embryos. As mentioned earlier M. sphenops is one of the species which normally inseminates the females of M. formosa, and it is probably the primary species involved in such activity' throughout most of the Río Tamesí drainage where M. formosa is found. Possible hybridization between M. sphenops and M. latipinna has been noted in the Tampico area by Hubbs (1933), but M. sphenops probably does not hybridize with M. latipunctata in nature. Stations: lB-H,J-L; 2A; 3A-D; 4A-G,J-L; 5A; 6A-E; 7A-D; 8A,B; 9A. Museum Nos.: CNHM 4483, 62648, 62659, 62670, 62679; TU 5567, 5582, 5584, 5592,5602,5604,5613,5618,5620,5630,5650,5664,5669,5680,5687. X iphophorus montezumae Jordan and Snyder. Montezuma swordtail Xiphophorus montezumae Jordan and Snyder. Jordan and Snyder (1901, Río Verde, near Rascón) Known only from the Pánuco-Tamesí drainage system. In the present study 85 specimens were obtained from the headwaters of the Río Sabinas and of the Río Frío. Downstream collections failed to yield specimens. In the Río Sabinas a small population of swordtails was encountered in the long side pool at the Nacimiento, and occasional individuals appeared in collections from ponds in the Arroyo La Flor above the Nacimiento and in a single backwater collection from the Sabinas above Storms' Ranch. In the headwaters of the Río Tamesí this species lives in clear weedy waters, especially in the vicinity of springs, and appears to have very·narrow habitat tolerances. Comparative habitat relations o.f this species and X. variatus are discussed in the next section. lt might be mentioned here, however, that certain individuals of the Río Sabinas population of X. montezumae approach X. variatus closely in phenotype. Studies by Gordon (1947) have demonstrated the genetic basis of tail spotting in X. maculatus from the Río Papaloapan in Vera Cruz. Similar tail spots appear in the closely related X. variatus of the Río Tamesí. Certain swordtails of the Río Sabinas exhibit tail spotting similar to that of X. variatus, although in the sw.ordtails the char­acters are much more weakly developed. This is an unusual characteristic among swordtails and is suggestive of past hybridization and introgression of X. variatus genes into the X. montezumae population. A genetic analysis should be carried out, especially in light of the following statement by Gordon ( 1953) who was familiar with the habitats of the species in the Río Pánuco: "The ecological isolation of these species evidently explains why not a single wild hybrid between any of them has been discovered, although thousands of specimens have been collected and critically studied. This takes on added significance when it is realized that under laboratory conditions, when their choice of mating partners is restricted, they are capable of producing hybrids of every possible combination." Meek (1904) mentioned that females taken in May had developing eggs and that one 44 mm female contained 16 eggs. Stations: 3C,D; 4A,B,E; 5A. Museum Nos.: CNHM 62660, 62680; TU 5600, 5663. Xiphophorus variatus (Meek). Variable platyfish Platypoecilus variatus Meek. Meek (1904, Forlón) Xiphophorus variatus (Meek). Gordon (1953, Rio Axtla) Known only from the Pánuco-Tamesí system. In the present study 173 specimens were obtained from the full length of the Arroyo Encino, several downstream areas of the Río Sabinas, the Río Frío near its Naci­miento, and two stations from the Río Boquilla. No specimens appeared in collections made from the Río Mante, the Río Guayalejo at Adjuntas, or from the Laguna de Chairel at Tampico. This little platyfish was never abundant in any of the collections. The distributional pattern, however, reveals that it prefers quiet, shallow vegetated backwaters, and in the Río Sabinas it was taken only in backwater areas around beds of the pondweed, Potamogeton illinoensis. In the Arroyo Encino it was generally found around aquatic vegetation or in areas where many exogenous Ieaves and branches were present in the water. This platyfish was taken from very turbid water in the Río Boquilla, and it was the only species inhabiting the spring above Encino (lA) when the water was low in oxygen (3.2 ppm) and high in carbon dioxide (28.0 ppm). As indicated by Willmer (1934) and others, this is an unfavorable combination for many fishes. Gordon (1953) has pointed out that in the Río Pánuco drainage X. variatus is usually found alone in the lowland areas, whereas in the uplands X . montezumae is taken exclusively in deep pools within the main channel of the river. In the inter­mediate areas a few individuals of both species may be found in shallow, sluggish backwaters and overflow pools. This is a fairly accurate description of the observed patterns of distribution in the Tamesí also, but, in the Río Sabinas at least, physio­graphic stream maturation occurs within a short distance so that apparently optima] habitat conditions for the two species occur within a few kilometers of each other. In the Río Frío the habitats may be closer or even contiguous, accounting for the fact that the two species were taken together from the Frío in sorne numbers. This foreshortening of the physiographic maturation in the headwater streams of the Tamesí and compression of habitats may also have resulted in introgressive hybri­dization as discussed in connection with the previous species. Mollienesia sphenops, a related poeciliid, was frequently taken in collections with X. variatus. Observations revealed that, although the two species often occupy the same general habitats, the platyfish tends to remain in the shallow weedy peripheral areas, whereas the molly frequents bottoms in slightly deeper waters and is more in­timately associated with rocks than with vegetation. Analysis of the digestive tracts of eleven specimens revealed little variability in food habits. In ali specimens unidentifiable mud or bottom ooze made up almost the entire bulk of the food, but traces of diatoms, desmids, filamentous green algae, and protozoa (Arcella, Dilflugia) were often encountered. Feeding apparently takes place during the day since specimens taken at 10:00 p.m. contained food only in the pos­terior half of the digestive tract. Most of the females examined from the spring col­lections possessed immature eggs, but one female taken May 8th carried eleven well developed young. Stations: lA,B,C,E,G,H,J,K,L,M; 2A; 3C; 4E,K,L; 5A; 6A,D; 8A. Museum Nos.: CNHM 4486, 62649, 62661, 62681; TU 5581, 5587, 5601, 5631, 5662, 5684. MuGILIDAE-Mullet Family Agorwstomus monticola (Bancroft). Mountain mullet Florida, Louisiana, Mexican coast from the Río Tamesí south through Central Amer­ica, and in Cuba, Puerto Rico and throughout West Indian islands; also known from Pacific coast. The mountain mullet has not previously been reported from the Río Tamesí drain­age, but from the known wide geographic distribution of the species in streams en­tering the Gulf of Mexico (Suttkus, 1956; Anderson, 1957b) its presence in suitable habitats would be anticipated. No specimens were taken in the present study, and the species is listed on the basis of nu.merous sight records throughout the upper reaches of the Río Sabinas. Specific sightings occurred in a pond of the Arroyo La Flor, in the Nacimiento and adjacent portions of the Río Sabinas, La Union, and severa) lo­calities near Storms' Ranch. All efforts to capture this elusive fish proved futile, and a single dried and mutilated specimen brought in by one of the natives clearly be­longed to the family Mugilidae but could not be distinguished further. Another mugi­lid which ascends streams of eastern Mexico is f oturus pichardi Poey, and sorne of the fast-swimming fishes seen in and around the Nacimiento of the Río Sabinas may eventually turn out to be this species. In the Río Sabinas, as elsewhere (Evermann and Marsh, 1900; Hildebrand, 1938; Anderson, 1957b), the mountain mullet seeks out areas of clear, fast-flowing water of rocky streams, and in the Sabinas it was the only fish species which consistently inhabited the rapids and riffie areas (although a cichlid utilized them). lt is a power­ful swimmer, and even though individuals or small groups were easily approached within a few feet, various types of gear (including a shotgun) failed to procure speci­mens. Hildebrand (1938) mentioned that in Panamá this mullet feeds on small or­ganisms such as insect larvae, sponges, and, apparently, ·algae. Stations: 3A; 4A,B,D,E,G. Mugil cephalus Linnaeus. Striped mullet, "Lisa" Mugil cephalus Linnaeus. Jordan and Dickerson (1908, Tampico) Widespread throughout tropical and subtropical shores of the world (known from ali continents and many oceanic islands) ; along the east coast of the Americas from Nova Scotia to Brazil and throughout the West Indies. In the present study during seining operations in the Laguna de Chairel the writer observed many striped mullets as they erupted from the marshes (seemingly from marginal areas above the water line) and as they leaped over the cork line of the seine. Only a single large specimen was taken. The striped mullet is known to ascend tropical streams for considerable distances above the influence of salt water. When shown the specimen from Tampico, the natives of Storms' Ranch quickly agreed that this fish is not infrequently seen in the headwaters of the Río Sabinas where it is callepeia 1951 ( 1) : 103-104. ----. 1%5. An annotated list of the American cyprinodontid fishes of the genus, Fundulus, with the description of Fundulus persimilis from Yucatán. Occ. Pap. Mus. Zoo!. Univ. Mich. 568: 1-.:25. ----. 1956. A new genus and species of cyprinodontid fish from San Luis Pot<>Sí, Mexico, with remarks on the subfamily Cyprinodontinae. Occ. Pap. Mus. Zoo!. Univ. Mich. 581: 1-17. ----. 1959. Variation, distribution, and relationships of the Mexican eleotrid fish Gobiomorus polylepis. Occ. Pap. Mus. Zoo!. Univ. Mich. 607: 1-11. Miller, R. R., and R. J. Schultz. 1959. All-female strains of the teleost fishes of the genus Poeciliopsis. Science 130(3389) : 1656-1657. Moody, W. D. 1950. A study of the natural history of the spotted trout, Cynoscion nebulosus, in the Cedar Key, Florida, area. Quart. J. Fla. Acad. Sci. '12('3): 147-171. Moore, G. A. 1957. Fishes, p. 31-210. In W. F. Blair et al. Vertebra tes of the United States, McGraw­Hill, New York. 819 p. Muir, J. M. 1936. Geology of the Tampico Region. Amer. Assoc. Petrol. Geol., Tulsa, Okla. 280 p. Myers, G. S. 1938. Fresh-water fishes and West Indian Zoogeography. Smithsonian Rep. (1937) : 339-364. ----. 1949a. Usage of anadromous, catadromous, and allied terms for migratory fishes. Copeia 1949(2): 89-97. ----.1949b. Salt-tolerance of fresh-water fish groups in relation to zoogeographical problems. Bijdragen Tot de Dierkunde 28: 315-322. Parr, A. E. '1927. Teleostean shore and shallow-water fishes from the Bahamas and Turks Island, from Scientific Results of the Third Oceanographic Expedition of the "Pawnee" 1927. Bull. Bingham oceanogr. Coll. 3(4): 1-148. Parsons, J. W., and J. B. Kimsey. '1954. A report on the Mississippi threadfin shad. Progr. Fish Cult. 16(41): '179-181. Pearson, John C. 1929. Natural history and conservation of the redfish and other commercial sciaenids on the Texas coast. Bull. U. S. Bur. Fish. 44(1928): 129-214. Price, W. A. 1954. Shorelines and coasts of the Gulf of Mexico, p. 39-65. In Gulf of Mexico, its origin, waters, and marine life. Fish. Bull. U. S. 89. 604 p. Regan, C. T. 1905. A revision of the American cichlid genus Cichlasoma and of the allied genera. Ann. Mag. Nat. Hist. 16{7th series): 60-77, 2215-243, 316-340, 433-445. ----. 1906-1908. Biología Centrali-Americana. Pisces {1906-1908). 203 p. ----. 1908. Description of a new fish of the genus Cichlasoma from Tampico, with notes on sorne other fishes from Mexico and the Caribbean Sea. Ann. Mag. Nat. Hist. 2{8th series):222-223. ----. '1913. A revision of the cyprinodont fishes of the sub-family Poeciliinae. Proc. Zoo!. Soc. London 1913 ('2) : 977-1018. Rehder, H. A. 1954. Mollusks, p. 469-474. In Gulf of Mexico, its origin, waters, and marine life. Fish. Bull. U. S. 89. 604 p. Reid, G .. K. 1954. An ec.ological stu~y of the Gulf of Mexico fishes in the vicinity of Cedar Key, Florida. Bull. Mar. Sc1. Gulf & Canb. 4(1): 1-94. ----. 1955. A summer study of the biology and ecology of East Bay, Texas. Part 11. The fish fauna of East Bay, the Gulf beach, and summary. Tex. J. Sci. 7 (4): 4130-456. ----. 1957. Biologic and hydrographic adjustment in a disturbed Gulf coast estuary. Limnol. and Oceanogr. 2(3) : 198-212. Robinson, D. T. 1959. The ichthyofauna of the lower Río Grande, Texas and Mexico. Copeia 1959{3): 253-256. Schultz, L. P. 1949. A further contribution to the ichthyology of Venezuela. Proc. U. S. Nat. Mus. 99: 1_:21'1. Simpson, D. G., and G. Gunter. 1956. Notes on habitats, systematic characters and life histories of Texas salt water Cyprinodontes. Tulane Stud. Zoo!. 4(4) : n'S-134. Fishes o/ the füo Tamesí Smith, H. M. 1907. The fishes of North Carolina. Raleigh, N. C., Geol. and Econ. Surv. II. 453 p. Suttkus, R. D. 1956. First record of the mountain mullet, Agonostomus monticola (Bancroft), in Louisiana. Proc. La. Acad. Sci. 19: 4~46. Taylor, W. R. 1954. Sketch of the character of the marine alga! vegetation of the shores of the Gulf of Mexico, p. 177-192. In Gulf of Mexico, its origin, waters, and marine life. Fish. Bull. U. S. 89, 604 p. Thorne, R. F. 1954. Flowering plants of the waters and shores of the Gulf of Mexico, p. 19~202. In Gulf of Mexico, its origin, waters, and marine life. Fish. Bull. U .S. 89, 604 p. Willmer, E. N. 1934. Sorne observations on the respiration of certain tropical fresh-water fishes. J. Exp. Biol. U: 28~306. ADDITIONAL RECENT PERTINENT LITERATURE Bigelow, H. B., and Wm. C. Schroeder. 1961. Carcharhinus nicaraugensis, a synonym of the bull shark, C. leucas. Copeia 1961 (3): 359. Haskins, C. P., E. F. Haskins, and R. E. Hewitt. 1960. Pseudogamy as ai;i evolutionary factor in the poeciliid fish Mollieni-sia formosa. Evolution 14(4): 47~83. Hildebrand, H. H. 1958. Estudios biológicos preliminares sobre la Laguna Madre de Tamaulipas. Ciencia 18 (7-8J: 151-173. Miller, R. R. 1960. Systematics and biology of the gizzard shad (Dorosoma cepedianum) and re­lated fishes. Fish. Bu!!., U. S. 173: 371-392. Rosen, D. E. 1960. Middle-American poeciliid fishes of the genus Xiphophorus. Bull. Fla. State Mus. 5(4J : 1-242. Mollusks of Alacran Reef, Campeche Bank, Mexico1 W1NNIE H. R1cE AND Loms S. KoRNICKER 2 lnstitute o/ Marine Science. The University o/ Texas, Port Aransas, Texas Ahstract Photographic plates and descriptions are given for a collection of 90 species of gastropods and 4ú species of pelecypods from Alacran Reef, Yucatan, Mexico, to aid in further study of the Campeche Bank. lntroduction Alacran Reef, a shelf atoll situated ahout 70 miles north of Yucatan, Mexico, is the largest reef on the Campeche Bank, which is a carbonate shelf extending about 125 miles into the Gulf of Mexico. The present paper describes mollusks collected on and in the immediate vicinity of Alacran Reef. The text is designed to facilitate identification of mollusks by investiga­tors working on the Campeche Bank, where because of the similarity of the bank to carbonate deposits in the geologic column, and bccause of the relatively few carbonate areas in today's seas, we can expect many geological and biological investigations dur­ing the ensuing years. In general the mollusks of A lacran Reef are similar to those of the W est lndies and the Florida Keys. A similar molluscan assemblage was reported from Blanquilla Reef, which is in the Gulf of Mexico about 60 miles from Tampico, Mexico (Moore, 1958). The Alacran Reef molluscan assemblage differs considerably from that living along the coast of Texas. The present paper includes descriptions of 90 species of Gastropods and 40 species of Pelecypods. The classification used in this paper is based principally on that of R. Tucker Abbott (American Seashells, 1955). In describing a shell, morphological characteristics of the shell considered taxonomically important by Abbott were stressed. Descriptions were based on shells from Alearan Reef in the mollusk collection at the lnstitute of Marine Science. Previous papers concerning the Campeche Bank include those of Agassiz (1878, 1879) , Rehder and Abbott (1951), Springer and Bullis ( 1956), and Kornicker, Bon et, Cann, and Hoskin ( 1959) . Systematic Descriptions GASTROPODA fISSURELLIDAE Genus Emarginula Lamarck 1801 Emarginula phrixodes Dall. 6 mm in length. Translucent white. Narrow slit on anterior margin. Base ornl. Finely cancellate sculpture of concentric cords, 20 to 20 radial ribs. Two specimens. Supported by a grant from the National Science Foundation, NSF G8902 Bio-geology of Alacran reef, L. S. Kornicker, principal investigator; and co·sponsored by the Institute de Geologia, Mexico, Dr. Guillermo P. Salas, Director. ~ Present address: Department of Meteorology and Oceanography, A and M College of Texas, College Station, Texas. Genus Diodora Gray 1821 Diodora minuta Lamarck. Plate 1, Fig. 3A, 3B. 7 to 9 mm. Thin, depressed. Base ellip· tical, raised slightly at center. Short front slope concave, back slope convex. Orifice narrow, trilobated. Exterior shiny; numerous finely beaded radial ribs. Color: white, many ribs entirely or partly black; interna! callus bounded by black line. Six spec· 1mens. Diodora listeri Orbigny. Plate 1, Fig. lA, lB. 19 to 38 mm. Shell large, heavy, conical, elevated. Base ovate. Orífice key-hole shaped. 38 to 40 strong, rounded radial ribs, alternately larger and smaller, crossed by 9 to 12 concentric threads to form small squares. Large scales or nodules produced where concentric threads and radial ribs cross. Color: dull white. Orífice blue-black. Nine specimens. Genus Lucapina Sowerby 1835 Lucapina sufjusa Reeve. Plate 1, Fig. 4A, 4B. 10 to 20 mm. Outline oblong. About 60 alternately large and small, radiating ribs, 9 to 13 raised concentric threads. Color : delicate mauve to pink. Orífice blue-black. Four specimens. Lucapina philippiana Finlay. Plate 1, Fig. 2A, 2B. 10 to 18 mm. Very depressed, narrow. Base oblong, sides subparallel, front slope straight, about half the length of convex posterior slope. Orífice large, oblong. Finely sculptured; about 38 close, radiating, al· ternately large and small ribs starting at orífice; ribs beaded by 8 or 9 raised con­centric threads. Color: dull white. Four specimens. Genus Hemitoma Swainson 1840 Hemitoma emarginata de Blainville. Plate 1, Fig. 7A, 7B. 10 to 18 mm. Apex sub­central, recurved posteriorly. Strong reticulate sculpture; nodules formed where radial ribs and concentric ridges cross. Primary ribs 8 to 10. Anterior rib single, prominent, ending in small notch at margin. 1 to 3 secondary ribs between primary· ribs. Anal groo ve extends from near apex to margin, ending in small notch. Color: white. Ten specimens. AcMAEIDAE Genus Acmaea Eschscholtz 1830 Acmaea jamaicensis Gmelin. Plate 1, Fig. 6A, 6B. 10 to 15 mm. Moderately high, thick; sides slightly convex. 15 to 20 rounded, white radial ribs on tan background. In­terior white, with tan, thickened central callus. Five specimens. Acmaea pustulata pulcherrima Guilding. Plate 1, Fig. 5A, 5B. 10 to 12 mm. Outline oval. Moderately flat, apex sharp. Shell thin, light pink in color, flecked with red. Six specimens. TuocHIDAE Genus Calliostoma Swainson 1840 Calliostoma zonamestum A. Adams. Plate 2, Fig. 7. 23 mm in diameter, 15 mm high. Sides of whorls flat. Periphery sharp, base flat. Dark brown line between each of 10 beaded, spiral threads. Umbilicus white, deep, smooth-sided. One specimen. Mollusks of Alacran Reef, Campeche Bank, Mexico Calliostoma jujubinum Gmelin. Plate 2, Fig. 6. 24 mm in diameter. Distinguished by swollen, rounded periphery of each whorl which inspire is located just ahove suture. Color: light tan with splotches of hrown. Umhilicus white, deep, narrow, smooth­sided, hordered by beaded spiral thread. Two specimens. Calliostoma sp. Plate 4, Fig. 18. 11 mm in length, not quite so high. lmperforate. Sculp­ture of numerous spiral, headed threads. Cream color, apical whorls with dark spiral cord below suture. Three specimens. Genus Te gula Lesson 1832 Tegula fasciata Born. 4 to 8 mm in diameter. 4 to 6 flat whorls. Color: white or cream; top of whorls splotched with deep pink to brown. Numerous fine, spiral threads. Umbilicus deep, round, smooth. Two teeth at hase of columella. Twelve specimens. TURBINIDAE Genus Cyclostrema Marryat 1818 Cyclostrema cancellatum Marryat. Plate 3, Fig. 21. 3 to 6 mm in diameter. 2 to 3 flat­topped whorls. Color: frosted white. Sculpture of 14 rounded axial ribs which en­circle entire whorl. Nodules formed at interseotion of axial ribs and smaller spiral cords. Fourth, fifth and sixth spiral cords situated respectively at top, middle and bottom of periphery of whorl. Umbilicus wide, deep. Aperture circular and thickened. Sixteen specimens collected from beach sand. Genus A rene H. and A. Adams 1854 Arene cf. cruentata Mühlfeld. Plate 4, Fig. 15. 6 to 8 mm in diameter, half as high. Color: white with small red dots on top of 4 to 5 angular whorls. Top of periphery· bearing series of horizontal, open, triangular spines; minor row of smaller spines at middle of periphery, every third spine pink to red. Strong, beaded, spiral cord at base of periphery. Aperture circular. Umbilicus round, deep; bordered by 3 spiral, beaded cords. Ten specimens collected from beach sand. Genus Turbo Linnaeus 1758 Turbo caületii Fischer and Bernard. Plate 2, Fig. 11, 12. Slightly more than 25 mm. Color: cream with dark brown, flame-like patches. Sculpture of irregular spiral cords; coarse on upper half of body whorl, finer and more numerous on base of shell. Lower lip projects downward. Aperture white. Callus on columella, heavy. Two specimens. Genus Astraea Roding 1798 Astraea longispina Lamarck. Plate 5, Fig. 18. 44 to 63 mm in diameter; low spire, base almost flat. Periphery of whorls with strong, flat, triangular spines. Aperture lustrous. Operculum calcareous. Six specimens. Astraea americana Gmelin. Plate 2, Fig. 14. 25 to 38 mm in length, not quite so wide. Color: cream. Spire elevated, sides flat. Sculpture of oblique radial folds; 5 to 8 fine spiral cords on base of shell. Operculum calcareous, thick, convex. Eight spec­1mens. Astraea caelata Gmelin. Plate 5, Fig. 17. 25 to 50 mm in diameter, not quite so high. Color: cream with splotches of pinkish-brown. 3 to 5 uneven spiral rows of hollow, scale-like spines on upper body whorl; base with 4 to 6 strong spiral cords. Entire body whorl with numerous oblique, finely fimbriated, radial lamellae. Operculum thick, convex, papillose. Seven specimens. PHASIANELLIDAE Genus Tricolia Risso 1826 Trú:olia cf. thalassú:ola Robertson. Plate 3, Fig. 19. About 4 mm. 6 rounded whorls. White with minute dots of greenish yellow; 7 patches of bright pink dots spirally ar· ranged below suture and at periphery. Numerous beach specimens. NERITIDAE Genus Nerita Linnaeus 1758 Neriw peloronta Linnaeus. Plate 2, Fig. 8. 16 to 18 mm. Color: grayish-yellow with streaks and patches of purple or black. Distinguished by red stain on parietal area which bears 1 to 2 white teeth. Sculpture of flat spiral ridges which become obscure on last half of body whorl. Operculum pink on underside; outerside smooth, orange colored on lower half, gray green, papillose on upper half. Four specimens. Nerita versicolor Gmelin. Plate 2, Fig. 10. 12 to 21 mm. Color: grayish·white with ir· regular zigzag rows of black and purplish-pink spots. Sculpture of strong, rounded, spiral ridges which extend to edge of outer lip. Parietal area yellowish-white with 4 teeth; middle 2 larger than outer ones. Operculum grayish-brown, concave, papil· lose on lower half. Ten specimens. Nerit.a tessellata Gmelin. Plate 2, Fig. 9. 10 to 18 mm. Color: chalky white with squarish black spots which form irregular checkered pattern. Apex pale yellow. Outer lip blue-white with black spots. Columellar lip with 2 weak teeth in middle; teeth incon­spicuous in immature specimens. This species characterized by black operculum which is papillose, slightly convex. Ten specimens. Genus Neritina Lamarck 1816 Neritina virginea Linnaeus. PI. 3, Fig. 7. 8 to 12 mm. Smooth, glossy. Color: olive green with varied patterns of grayish-white; sorne spirally banded, others spotted or mottled. Columellar area smooth, white, convex with 6 to 12 small, irregular teeth. Operculum black. Ten specimens. Genus Smaragdia Issel 1869 Smaragdia viridis Linnaeus. PI. 4, Fig. 13. 3 to 7 mm. Pale green in color with short, white, radial streaks. Columellar lip white with several small, irregular teeth. Twenty­four specimens collected from beach sand. LITTORINIDAE Genus Littorina Ferussac 1821 Littorina zú:zac Gmelin. Plate 3, Fig. 6, 8. 8 to 18 mm. Shell bluish-white with numerous zigzag, oblique lines of dark brown. Aperture purplish-brown. Well defined keel near base of body whorl. Operculum dark brown. Six specimens. (Ahbott gives the length of females of this species about 1 inch, higher than wide, smoothish; male shells about 112 inch, as high as wide with strong spiral grooves.) Genus Nodilittorina Martens 1897 Nodilittorina tuberculata Menke. Plate 3, Fig. 4. 10 to 15 mm. 7 to 8 whorls. Shell rounded at base. Nuclear whorls have fine, spiral threads. Succeeding whorls bear 2 or 3 spiral rows of small, pointed nodules. Largest nodules on second and third row. 7 rows of nodules on body whorl. Columella flattened and dished out. Outer lip pro· jects below columella. Color: brownish-gray, nodules whitish; columella and aper­ture dark brown. Operculum paucispiral, dark brown, chitinous. Seven specimens. RissOIDAE Genus Rissoina Orbigny 1840 Rissoina chesneli Michaud. Plate 3, Fig. 16. 3 mm. 5 glossy white whorls with 12 radial ribs. Rissoina multicostata C. B. Adams. Plate 3, Fig. 14. 4 to 5 mm. Shell white with 5 to 7 whorls. 21 axial ribs, weaker spiral cords. Ribs disappear on base; spiral threads strongest on base. Rissoina cancellata Philippi. Plate 3, Fig. 13. 5 to 7 mm. White, 6 to 8 whorls. Sculp­ture strongly cancellate. Depressed interspaces large, square. Rissoina browniana Orbigny. 4 to 5 mm. Smooth, glossy white. VERMETIDAE Genus Petaloconchus H. C. Lea 1843 Petaloconchus cf. nigricans Dall. Plate 2, Fig. 18. Closely packed, irregular mass, each tube about 2 mm in diameter. Color: dirty gray. Longitudinal sculpture of finely beaded cords. SILIQUARIIDAE Genus V ermicularia Lamarck 1799 Vermicularia knorri Deshayes. Plate 2, Fig. 16, 17. 19 to 50 mm. Evenly coiled portions translucent white, subsequent whorls brown. Six specimens. CAECIDAE Genus Caecum Fleming 1817 Caecum cooperi S. Smith. Plate 3, Fig. 22. 3.5 mm. Cream to tan in color, glossy. Sculpture of about 15 longitudinal ribs; strong, raised axial rings near aperture form cancellated sculpture on anterior end. Pointed prong on apical plug. Caecum floridanum Stimpson. Plate 3, Fig. 23. 2 to 4 mm. Dull white. 20 to 30 strong axial rings, the last 3 or 4 much enlarged. Slightly recessed apical plug with pointed prong. Caecum nebulosum Rehder. Plate 3, Fig. 24. Slightly more than 2 mm. Translucent white with opaque mottling. Not swollen at center. Aperture oblique. Apical plug with weak projection on highest side. MODULIDAE Genus Modulus Gray 1842 Modulus modulus Linnaeus. Plate 4, Fig. 16. 5 to 7 mm in diameter. Shell umbilicate. Periphery of body whorl angulate. Sculpture variable; top of whorls with axial ribs or only spiral threads. Base with 4 to 6 spiral cords. Tooth at base of columella. Color: white with brown spots on spiral cords. Twenty-four specimens. POTAMIDIDAE Genus Batillaria Benson 1842 Batillaria minima Gmelin. Plate 4, Fig. 14. 3 to 9 mm. Color: rusty to blackish·brown. Apex eroded, chalky. Irregular spiral cords, finely nodulose. Aperture dark brown. Short siphonal canal twisted to left. Operculum multispiral. Twenty-four specimens. CERITHIIDAE Genus Cerithium Bruguiere 1789 Cerithium literatum Born. Plate 2, Fig. 2. 10 to 30 mm in length, half as wide. Color: white with spiral rows of dark brown dashes. Spiral row of 8 to 12 sharp nodules just below suture. Eight specimens. Cerithium variabile C. B. Adaras. Plate 4, Fig. 3. 12 to 15 mm. Color: white with brown mottlings. Sculpture of 3 irregularly beaded, spiral cords. 1 to 2 former varices on each whorl. Three specimens. Cerithium algicola C. B. Adams. Plate 3, Fig. 10. 20 to 22 mm. Color: white with brown mottlings. Each whorl has middle spiral row of 9 to 12 beads, large, sharply pointed. Three specimens. Cerithium eburneum Bruguiere. Plate 4, Fig. 20, 20 to 24 mm. Color: white with tan splotches. 4 to 5 spiral rows of 18 to 22 beads on each whorl, center row only slightly larger; beads rounded, not sharp or pointed. Former varies on each whorl. Two specimens. Genus Seila A. Adams 1861 Seila adamsi H. C. Lea. Plate 3, Fig. 12. 1 beachworn specimen 8 mm. Color: yellow. Slender, flat-sided whorls. Sculpture of close, smooth, squarish, spiral cords. Genus Alaba H. and A. Adams 1853 Alaba sp. Plate 3, Fig. 11. 7 mm. 9 convex whorls; nuclear whorls broken. Sculpture of spiral grooves, strongest on lower half of each whorl. Several former varices. Shell translucent white. base of body whorl. Operculum dark brown. Six specimens. (Abbott gives the length of fema les of this species about 1 inch, higher than wide, smoothish; male shells about 1h inch, as high as wide with strong spiral grooves.) Genus Nodilittorina Martens 1897 Nodilittorina tuberculata Menke. Plate 3, Fig. 4. 10 to 15 mm. 7 to 8 whorls. Shell rounded at base. Nuclear whorls have fine, spiral threads. Succeeding whorls bear 2 or 3 spiral rows of small, pointed nodules. Largest nodules on second and third row. 7 rows of nodules on body whorl. Columella flattened and dished out. Outer lip pro­jects below columella. Color: brownish-gray, nodules whitish; columella and aper­ture dark brown. Operculum paucispiral, dark brown, chitinous. Seven specimens. R1ssornAE Genus Rissoina Orbigny 1840 Rissoina chesneli Michaud. Plate 3, Fig. 16. 3 mm. 5 glossy white whorls with 12 radial ribs. Rissoina multicostata C. B. Adams. Plate 3, Fig. 14. 4 to 5 mm. Shell white with 5 to 7 whorls. 21 axial ribs, weaker spiral cords. Ribs disappear on base; spiral threads strongest on base. Rissoina cancellata Philippi. Plate 3, Fig. 13. 5 to 7 mm. White, 6 to 8 whorls. Sculp­ture strongly c·ancellate. Depressed interspaces large, square. Rissoina browniana Orbigny. 4 to 5 mm. Smooth, glossy white. VERMETIDAE Genus Petaloconchus H. C. Lea 1843 Petaloconchus cf. nigricans Dall. Plate 2, Fig. 18. Closely packed, irregular mass, each tube about 2 mm in diameter. Color: dirty gray. Longitudinal sculpture of finely beaded cords. SILIQUARIIDAE Genus V ermicularia Lamarck 1799 Vermicularia knorri Deshayes. Plate 2, Fig. 16, 17. 19 to 50 mm. Evenly coiled portions translucent white, subsequent whorls brown. Six specimens. CAECIDAE Genus Caecum Fleming 1817 Caecum cooperi S. Smith. Plate 3, Fig. 22. 3.5 mm. Cream to tan in color, glossy. Sculpture of about 15 longitudinal ribs; strong, raised axial rings near aperture form cancellated sculpture on anterior end. Pointed prong on apical plug. Caecum floridanum Stimpson. Plate 3, Fig. 23. 2 to 4 mm. Dull white. 20 to 30 strong axial rings, the last 3 or 4 much enlarged. Slightly recessed apical plug with pointed prong. Caecum nebulosum Rehder. Plate 3, Fig. 24. Slightly more than 2 mm. Translucent white with opaque mottling. Not swollen at center. Aperture oblique. Apical plug with weak projection on highest side. MODULIDAE Genus Modulus Gray 1842 Modulus modulus Linnaeus. Plate 4, Fig. 16. 5 to 7 mm in diameter. Shell umbilicate. Periphery of hody whorl angulate. Sculpture variable; top of whorls with axial ribs or only spiral threads. Base with 4 to 6 spiral cords. Tooth at base of columella. Color: white with brown spots on spiral cords. Twenty-four specimens. POTAMIDIDAE Genus Batillaria Benson 1842 Batülaria minima Gmelin. Plate 4, Fig. 14. 3 to 9 mm. Color: rusty to blackish-brown. Apex eroded, chalky. Irregular spiral cords, finely nodulose. Aperture dark brown. Short siphonal canal twisted to left. Operculum multispiral. Twenty-four specimens. CERITHIIDAE Genus CeriJ;hium Bruguiere 1789 Cerithium literatum Born. Plate 2, Fig. 2. 10 to 30 mm in length, half as wide. Color: white with spiral rows of dark brown dashes. Spiral row of 8 to 12 sharp nodules just below suture. Eight specimens. Cerithium variabile C. B. Adams. Plate 4, Fig. 3. 12 to 15 mm. Color: white with brown mottlings. Sculpture of 3 irregularly beaded, spiral cords. 1 to 2 former varices on each whorl. Three specimens. Cerithium algicola C. B. Adams. Plate 3, Fig. 10. 20 to 22 mm. Color: white with brown mottlings. Each whorl has middle spiral row of 9 to 12 beads, large, sharply pointed. Three specimens. Cerithium eburneum Bruguiere. Plate 4, Fig. 20, 20 to 24 mm. Color: white with tan splotches. 4 to 5 spiral rows of 18 to 22 beads on each whorl, center row only slightly larger; beads rounded, not sharp or pointed. Former varies on each whorl. Two specimens. Genus Seila A. Adams 1861 Seila adamsi H. C. Lea. Plate 3, Fig. 12. 1 beachworn specimen 8 mm. Color: yellow. Slender, flat-sided whorls. Sculpture of close, smooth, squarish, spiral cords. Genus Alaba H. and A. Adams 1853 Alaba sp. Plate 3, Fig. 11. 7 mm. 9 convex whorls; nuclear whorls broken. Sculpture of spiral grooves, strongest on lower half of each whorl. Several former varices. Shell translucent white. TRIPHORIDAE Genus Triphora Blainville 1828 Triphora decorata C. B. Adams. Plate 4, Figure 4. 2 beachworn specimens 10, 12 mm. Sinistral, elongated, flat-sided. 3 evenly beaded, spiral cords on each whorl. White with irregular, radial streaks of brown. EPITONIIDAE Genus Epitonium Roding 1798 Epitonium sp. Plate 4, Fig. 19. 12 mm. Glossy white. Axial costae 12, high, thin, sharp. EuLIMIDAE Genus Balcis Leach 1847 Balcis sp. Plate 3, Fig. 17. 6 mm. Glossy white. Conic, body whorl rounded. Outer lip thin, sharp. HIPPONICIDAE Genus Cheilea Modeer 1793 Cheilea equestris Linnaeus. Plate 1, Fig. 8A, 8B. 5 to 12 mm. Cap-shaped; frosted white. Fragile, internal, tube-like structure, anterior third cut away, attached slightly off center. Exterior with sculpture of delicate, concentric, fimbriated lamellae. Four specimens. Genus Hipponix Defrance 1819 Hipponix antiquatus Linnaeus. Plate 1, Fig. 9A, 9B. 5 to 12 mm in diameter. Cap­shaped. Spire deflected back and downward. Exterior appears concentrically lamel­lated. Muscle scar horse-shoe shaped. Color: dull white. Ten specimens. CAL YPTRAEIDAE Genus Crepidula Lamarck 1799 Crepidula plana Say. 20 mm. Oblong, thin, very flat. Upper side dull white, under­side glossy. Two specimens. STROMBIDAE Genus Strombus Linnaeus 1758 Strombus gigas Linnaeus. PI. 5, Fig. 1, 2. 63 to 173 mm. Color: dark cream or tan ex­ternally, smaller specimens mottled with brown; aperture pink. Large, fairly sharp spines on shoulder of whorls. Outer lip thin; shell relatively light in weight. The flar­ing lip, characteristic of this species, is undeveloped. Fourteen immature specimens. Strombus costatus Gmelin. Plate 5, Fig. 6, 9. 100 to 150 mm. Shell heavy·, with low, blunt spines; the last 3 or 4 on body whorl much enlarged. Color varíes from cream to burnt orange externally; aperture china-white. Parietal wall and thick outer lip highly glazed with greenish·silver enamel. Six specimens. Strombus raninus Gmelin. Plate 5, Fig. 5, 10. 88 mm. Grayish-white in color with choc­olate brown mottling. Aperture salmon pink. Parietal wall and outer lip covered with an aluminium-like glaze. Blunt spines on shoulder of body whorl, last 2 conspicu­ously larger. Numerous spiral lines on last two-thirds of body whorl. Thick outer lip extends above shoulder of body whorl into a short blunt wing which is not as high as spire of shell. Two specimens. ERATOIDAE Genus Trivia Broderip 1837 Trivia sufjusa Gray. Plate 4, Fig. 17. 6 to 12 mm. Elongate-globular. Color: pale pink with 3 brown splotches on each side of dorsal groove. 12 to 20 finely beaded riblets cross pink outer lip. Eight specimens. Trivia quadripunctata Gray. 6 to 8 mm. Elongate-globular. Color: bright pink with 2 to 3 small brown spots along short dorsal groove. 19 to 21 smooth ribs cross outer lip. ÜVULIDAE Genus Cyphoma Roding 1798 Cyphoma gibbosum Linnaeus. Plate 2, Fig. SA, SB. 30 and 35 mm. Porcelaneous. Color: pinkish-buff except for whitish rectangle on back; aperture white. Two specimens. NATICIDAE Genus Polinices Montfort 1810 Polinices lacteus Guilding. 8 to 20 mm in height. Six specimens, all beach worn. Ovate. Glossy·, milk-white. Umbilicus partially closed by heavy parietal callus. Genus Sinum Roding 1798 Sinum perspectivum Say. Plate 3, Fig. 20. One specimen, 27 mm in diameter. Auri­form; aperture widely flared. Color: white, interior glossy. Sculpture of wavy spiral threads crossed by fine growth Jines. Genus Natica Scopoli 1777 Natica canrena Linnaeus. Plate 5, Fig. 15. One specimen. 38 mm. Color: ivory with brown, wavy, axial lines. 4 spiral rows of brown, arrow-shaped marks. Shell smooth except for weak wrinkles near suture. White callus partially fills deep umbilicus. Natica lívida Pfeiffer. 12 mm. Shell moderately thin; glossy smooth. Color: light gray with 2 weak spiral bands of tan. Umbilicus partially closed by light brown callus. One specimen. CASSIDIDAE Genus Cassis Scopoli 1777 Cassis madagascariensis spinella Clench. One beach worn specimen, 213 mm. Color: cream. 3 spiral rows of small, rounded nodules on body whorl; top row largest. Parietal area blackish-brown between ridge-like teeth. Light brown inside aperture. Outer lip color of body whorl, brown between teeth. CYMATIIDAE Genus Cymatium Roding 1798 Cymatium pileare Linnaeus. Plate 5, Fig. 19. One beachworn specimen, 50 mm. Sculp­ture of irregular, squarish, weakly beaded, spiral cords. Color: white with bands of light brown; outer lip tan between lighter colored teeth which are grouped in pairs. Parietal wall brown between numerous, irregular, white folds. Cymatium caribbaeum Clench and Turner. Plate 2, Fig. 15. One worn specimen, 44 mm. Body whorl globular, shoulders angulate; previous whorls flat-sided. Apical whorls cancellate; strongly beaded spiral cords on body whorl. 1 former varix. Thick outer lip with 7 large, single, white teeth. Color: light tan. Cymatium gemmatum Reeve. Plate 2, Fig. l. One specimen, 31 mm. Shell white or cream, covered with thin straw colored periostracum, smooth over most of shell but producing fringed blades on axial ribs. Whorls squarish at shoulders. Spiral sculpture of finely beaded cords. Body whorl with 6 brown nodules at periphery. 1 varix. Aper­ture elongate-oval, pale apricot within; large columellar tooth at upper edge. Thick­ened outer lip with 12 teeth grouped in pairs. Cymatium nicobaricum Roding. 60 mm; nucleus broken. Spire extended, whorls shouldered. Coarse sculpture of 6 irregular, nodulose, spiral ribs interspaced with 2 smaller cords. Variable axial folds between varices. Color: ashen gray; aperture bright orange, with 7, single, ridge-like, white teeth. One specimen. ToNNIDAE Genus Tonna Brunnich 1772 Tonna macuwsa Dillwyn. Plate 5, Fig. 13. One specimen 69 mm. Shell thin. Color: cream mottled with light brown. Nuclear whorls golden brown, smooth. Numerous broad, flat, spiral cords. This species is longer than wide. Tonna galea Linnaeus. Plate 5, Fig. 11, 16. 50 to 75 mm. Globular, fairly thin. Nuclear whorls smooth, dark brown. 18 to 21 broad, flat, spiral ribs; fine spiral cord between each rib on upper half of body whorl. Fresh specimens cream to tan in color, sorne slightly mottled with brown; older shells bleached white. Eighteen specimens. MURICIDAE Genus Murex Linnaeus 1758 Murex pomum Gmelin. 63 mm. One beach worn specimen. Shell thick, dirty white. 2 short axial folds between each of 3 varices. Dark brown spot at upper edge of parietal area. Outer lip crenulate, with 3 evenly spaced brown spots. Genus Drupa Roding 1798 Drupa noduwsa C. B. Adams. Plate 3, Fig. 5. 10 to 18 mm. Elongate. Sculpture of round, black nodules, axially aligned. Aperture dark purple. Thick outer lip with 4 white teeth. Twelve specimens. Genus T hais Roding 1 í98 Thais deltoidea Lamarck. Plate 2, Fig. 13. 31 to 44 mm. Shells grayish·white. Spiral row of large, blunt spines at shoulder O'Í body whorl. Sorne specimens show second row of much smaller spines below first. Aper!ure china-white; parietal area tinted lavender. N1ne specimens. CoLUMBELLIDAE Genus Columbella Lamarck 1799 Columbella mercatorÚL Linnaeús. Pl. 4, Fig. 5. 8 to 15 mm. Color: white, with broken, spiral streaks of brown. Sculpture of numerous spiral grooves. Aperture long, narrow. 10 to 12 white teeth on outer lip which is thickened, particularly in the middle. Fifty specimens. Genus Nitidella Swainson 1840 Nitidella nitidula Sowerby. Plate 4, Fig. 7. One specimen. 10 mm. Color: cream with orange splotches. 7 sloping whorls, no shoulders. Spire sharply pointed. Surface of shell smoothish, faint spiral threads on lower one-fourth of last whorl. Outer lip only slightly thickened. Genus Anachis H. and A. Adams 1853 Anachis pulchella Sowerby. Plate 4, Fig. 6. 8 to 10 mm. Translucent, lightly mottled with yellow. Numerous low, axial ribs crossed by spiral striae. Ribs strongest on upper whorls. Only beach specimens collected. BuccrNIDAE Genus Bailya M. Smith 1944 Bailya intricata Dall. Plate 4, Fig. l. One beach specimen. 12 mm. Frosted white, with 2 faint brownish, spfral bands on body whorl. 6 shouldered whorls; nuclear whorls broken. Surface cancellate; body whorl with 12 axial riblets crossed by 8 spiral cords with smaller threads between; beaded at intersection. Outer lip with rounded varix. Genus Cantharus Roding 1798 Cantharus tinctus Conrad. 23 to 25 mm. Sloping whorls. Small posterior canal. Outer lip thickened. Sculpture of 10 axial folds crossed by numerous spiral threads. Color: grayish-brown with dark blue splotches on glazed parietal wall. Two specimens. MELONGENIDAE Genus Cantharus Rod1ng 1798 Busycon contrarium Conrad. Plate 5, Fig. 12. 106 to 193 mm. Sinistral. Shell relatively heavy. Spire low, whorls shouldered. Spiral row of spines on shoulder, largest on body whorl. Surface covered with wavy, spiral threads. Color: cream to dark tan with white spiral band at center of body whorl. Color inside aperture varies from deep cream to orange. Eight specimens. Busycon spiratum Lamarck. Plate 5, Fig. 7. 31 to 113 mm. Shell thin, spire flattened. Shoulders slightly keeled. Suture marked by deep, narrow channel. Sculpture of very fine, spiral threads. White with 2 to 3 spiral rows of brown splotches. Fifteen speci­mens. NASSARIIDAE Genus N assarius Dumeril 1806 Nassarius ambiguus Pultney. Plate 4, Fig. 2. 6 to 12 mm. Color: white with 2 narrow bands of light brown, obscure in these beach specimens. Relatively light shelled. Whorls shouldered. 10 to 12 axial ribs on each whorl; numerous small, spiral threads. Eight specimens. f ASCIOLARIIDAE Genus Leucozonia Gray 1847 Leucozonia nassa Gmelin. Plate 5, Fig. 14. 31 to 44 mm. Shell thick; shoulders well· rounded, marked by obscure nodules which are more prominent on penultimate whorl. 4 columellar folds. Color: dark brown; aperture dark cream within. Six specimens. Genus F asciolaria Lamarck 1799 Fasciolaria tulipa Linnaeus. Plate 5, Fig. 4, 8. 56 to 131 mm. Characterized by 2 or 3 spiral grooves just below suture. Gray with broken spiral lines, blotches of blackish­brown. lnside aperture glossy cream color. Six specimens. Genus Pleuroploca P. Fischer 1884 Pleuroploca gigantea Kiener. Two beach worn specimens, each about 250 mm. Nuclear whorls broken. Yellowish-white. Shouldered whorls with 8 large nodules on shoulder of body whorl. Coarse, irregular, spiral ribs. XANCIDAE Genus Xancus Roding 1798 Xancus angulatus Solander. Plate 5, Fig. 3. One specimen, 113 mm. Shell thick, heavy, cream colored, interior tinged with pale pink. 3 strong, widely spaced columellar folds. Spiral ridge inside aperture about middle of outer lip. ÜLIVIDAE Genus Olivella Swainson 1831 Olivella nivea Gmelin. Plate 4, Fig. 9. 5 to 14 mm. Elongate. 5 to 6 whorls. Apex pointed. Shell glossy white; nucleus tan in fresh specimens. Numerous columella folds. MITRIDAE Genus Pusia Swainson 1840 Pusia gemmata Sowerby. Plate 3, Fig. 15. 5 to 6 mm in length. Beach specimens. Tan, with white spiral band bearing 11 to 13 nodules on each whorl. MARGINELLIDAE Genus Prunum Herrmannsen 1852 Prunum labiatum Valenciennes. Plate 2, Fig. 4. Porcelaneous. Outer lip thickened, dull orange, tiny teeth on inner edge. Body whorl grayish-white with 3 cloudy, spiral bands of dull lavender. 25 to 30 mm. Five specimens. Prunum guttatum Dillwyn. Plate 3, Fig. l. One specimen, 15 mm. Body whorl grayish­white, irregularly spotted with opaque white dots. Stout outer lip smooth. Color: white, with three brown spots on lower half. 4 strong, columellar folds. Genus Hyalina Schumacher 1817 Hyalina avena Valenciennes. Plate 4, Fig. 8. 9 to 11 mm. lvory colored with severa! obscure bands of light tan. Shell slender, spire short. Outer lip rolled in, smooth. Aperture narrow above, wide below. Four slanting columellar folds. Four specimens collected from beach sand. Genus Persicula Schumacher 1817 Persicula sp. Plate 4, Fig. 11. 5 to 6 mm. Apical area slightly' concave, sealed over by thin callus. 20 to 25 tiny teeth inside outer lip. 5 to 6 columellar folds; first 2 folds very weak. Shell glossy white with several spiral rows of brown arrow-shaped marks. Four specimens. CONIDAE Genus Conus Linnaeus 1758 Conus spurius atlanticus Clench. One specimen, 59 mm. Spire slightly elevated in the center. Shell smooth, white with spiral rows of squarish orange spots and blotches. Aperture white. Conus mus Hwass. Plate 2, Fig. 3. One specimen, 31 mm. Spire moderately elevated. Color: mottled grayish-brown. Low, irregular, white knobs on shoulder. 2 wide, spiral, brown bands inside aperture. Periostracum thick, velvety, dull brown. TURRIDAE Genus Glyphoturris W oodring 1928 Glyphoturris qua,drata rugirima Dall. About 6 mm. Frosted white. Sculpture of high axial ribs, 8 on body whorl. Ribs sharply angulated at center of each whorl and crossed by faintly beaded, spiral threads. One specimen. BuLLIDAE Genus Bulla Linnaeus 1758 Bulla sp. Plate 3, Fig. 2. 8 to 14 mm. Color: white to tan with brown mottling. Callus white. Spiral grooves well·marked toward base of shell and within apical perforation. Fifteen specimens. ATYIDAE Genus H aminoea Turton and Kingston 1830 Haminoea succinea Conrad. Plate 4, Fig. 12. One specimen, 7 mm. Translucent white. Apertura! lip rises on right side of perforation, not angled. Sides of whorls flattish. Numerous spiral grooves. Genus Atys Montfort 1810 Atys caribaea Orbigny. Plate 3, Fig. 3. 5 to 6 mm. Elongate-oval. Translucent milk­white. Central part of shell smooth; about 12 very fine, incised spiral lines at both ends. Spire concealed. Aperture long, narrow with outer lip rising well above top of shell and projecting below columella. Six specimens collected from beach. Atys sandersoni Dall. Plate 4, Fig. 10. 5 to 8 mm. Similar to A. caribaea but with flatter sides, more numerous, finer, spiral lines at each end. Ten specimens. RETUSIDAE Genus Retusa Brown 1827 Retusa canaliculata Say. 4 to 5 mm. Oblong, flat·sided, smooth, glossy white. Tiny pimple-like nucleus. Aperture narrow at posterior end, wider anteriorly. Outer lip thin. Six specimens. PYRAMIDELLIDAE Genus Odostomia Fleming 1817 Odostomia sp. Plate 3, Fig. 18. 2 mm. Frosted white. Sculpture of strong, squarish, faintl y beaded spiral cords. Two specimens. PELECYPODA ARCIDAE Genus Arca Linnaeus 1758 Arca zebra Swainson. Plate 6, Fig. 8A, 8B. 44 to 62 mm in length, about half as high. Color: light brown with zebra-stripes of dark brown. Radial ribs only. Relatively small bysal gap. Beaks widely separated, with broad, flat area between. Two spec­1mens. Arca umbonata Lamarck. Plate 6, Fig. 7A, 7B. 37 to 53 mm, box-like, elongate. Shell tan to brown mottled with darker brown. Interior lighter in color. Beaks widely separated with concave area between. Numerous irregular, beaded radial ribs. Large bysal gap. Periostracum very heavy on live specimens. Seven specimens. Genus Barbati,a Gray 1847 Barbatia domingensis Lamarck. Plate 9, Fig. 7A, 7B. 20 mm. Color: grayish-white. Shell moderately inflated. Reticulated sculpture. lnner margins denticulate. One specimen. Barbatia cancellarÜL Lamarck. Plate 8, Fig. 12A, 12B. 15 to 35 mm. Flattish, fairly thin. Sculpture of numerous, well beaded, axial cords. Dark purplish-brown in color. Ten specimens. Genus Arcopsis von Koenen 1885 Arcopsis adamsi E. A. Smith. Plate 9, Fig. 8. One specimen, 6 mm. Oblong, inflated. Color: white. Cancellate sculpture. Small brown diamond-shaped ligament between umbones. GLYCYMERIDAE Genus Glycymeris Da Costa 1778 Glycymeris pectinata Gmelin. Plate 9, Fig. 6A, 6B. One beach worn specimen, 20 mm. Sculpture of 22 smooth, radial ribs. Color: gray-white with concentric line of brown midway of valves; flecks of brown scattered over shell. MYTILIDAE Genus M odiolus Lamarck 1799 Modiolus americanus Leach. Plate 7, Fig. 7A, 7B. 21h to 31h inches. Smooth, except for growth lines. Shell white, flushed with rose or purple. Interior iridescent with externa} color visible. Fresh specimens covered with dark brown periostracum, glossy on an­terior area, beard-like at posterior margin. Ten specimens. Genus Brachidontes Swainson 1840 Brachidontes citrinus Roding. Plate 8, Fig. 13. 31 mm, narrow. Color white with yel­low periostracum. Sculpture of numerous, fine, radial, riblets: 1 specimen. Genus Lithophaga Roding 1798 Lithophaga nigra Orbigny. Plate 7, Fig. 8A, 8B. 40 to 53 mm, cylindrical. Brownish­black outside, iridescent blue-white inside. Weak vertical lines on lower anterior third of each val ve, remainder of shell smooth. Four specimens. ISOGNOMONIDAE Genus Isognomon Solander 1786 Isognomon alatus Gmelin. Plate 9, Fig. UA, UB. 13 to 32 mm. Roughly oval in out­line. Right valve flat or slightly concave, left valve convex. Hinge with 4 to 6 oblong sockets. Exterior color varies from dull white to purple; interior nacreous. Six spec­ imens. l sognomon radiatus Anton. 82 mm. Elongate. Exterior coarsely lamellated; interior nacreous except on ventral margins. Right valve concave, left valve convex. Hinge short, 5 small oblong sockets. Color: yellowish-gray with purplish radial streaks on convex val ve. One specimen. lsognomon cf. bicolor C. B. Adams. Plate 9, Fig. lOA, lOB. 15 mm in height, 10 mm wide. Valves slightly inflated. Exterior smooth except for irregular growth lines. Color: dull gray. Hinge has 7 oblong sockets. Interior of both valves with squarish, saucer-like depression, located in upper half; outlined by raised, fairly sharp rim. Depressed area and rim opalescent; wide ventral margin dark purple. One specimen. PTERIIDAE Genus Pinctada Roding 1798 Pinctada radiata Leach. Plate 6, Fig. 6A, 6B, 9. 37 to 56 mm. Thin shelled, slightly inflated. Narrow ligament, center third of hinge line. Exterior rough with weak, flaky lamellations; interior nacreous. Color varíes from dull white to pale brown, mottled or rayed with purple. Ten specimens. PINNIDAE Genus Pinna Linnaeus 1758 Pinna carnea Gmelin. 88 to 288 mm. Color: flesh pink to deep burnt orange. Shell thin, inflated. Posterior end rounded, gaping. About 10 radial ridges with and without large open spines. Six specimens. PECTINIDAE Genus Lyropecten Conrad 1862 Lyropecten antillarum Recluz. Plate 8, Fig. 7 A, 7B. 20 mm in length, about as wide. Color: white. Shell thin, flat, with 10 smooth, rounded, radial ribs. Two specimens. Genus Chlamys Roding 1798 Chlamys imbricata Gmelin. Plate 8, Fig. 2, 5. 21 to 40 mm in height, notas wide. Upper valve nearly f!at, lower valve convex. 9 to 10 radial ribs, each with evenly spaced, hollow knobs; where broken, these knobs appear as cup-shaped scales. Color: white or pinkish with small red spots; interior yellowish, sorne specimens white. Ten specimens. SPONDYLIDAE Genus Spondylus Linnaeus 1758 Spondylus americanus Hermann. Plate 8, Fig. 9A, 9B. 1 upper valve, 25 mm in diameter; thip~ Exterior purplish-red, interior iridescent. Numerous closely set spines, nearly ·:~ efect, varying from flat to needle-like in shape. LIMIDAE Genus Lima Bruguiere 1797 Lima scabra Bom. Plate 7, Fig. 4A, 4B. 50 to 75 rilm in height. Elongate-oval in out­line. C<>lor: whit~ or yellowish. Sculpture of radial ribs bearing short, irregularly spaced, shingle-like scales. Long bysal gap. Three specimens. Lima lima Linnaeus. Plate 8, Fig. 8A, 8B..10 to 34 mm in height. Color: pure white . . Anterior ear much larger than posterior one, giv:ing apex slightly pointed appéarance. Sculpture of about 28, even, radial ribs bearing nuinerous sharp, ere~t scale~. Twelve specimens. · " Lima pe/lucida C. B. Adams. 25 mm. Shell fragile.; translucent white. Gapi~g a~teriorly and posteriorly. Sculpture of numerous, fine, radial threads. Beaks smÓÓth, centrally located. One specimen. ÜSTREIDAE Gemís Ostrea Linnaeus 1758 Ostrea frons Linnaeus. Plate 6, Fig. 4A, 4B, 4C. One articulated speci:r.nen, about 50 mm in length, half ·as wide; attached to twig by finger-like processe~. Upper valve with broad, longitudinal mid-rib. Margins sharply plicate. Minute pimples on inner margin of upper valve. Exterior purple, interior iridescent. CARDITIDAE Genus V enericardia Conrad 1867 Venericardia sp. Plate 9, Fig. 9A, 9B. 3 mm in length, about as high. Shell thick with 17 to 18 strong, evenly beaded, radial ribs. Beaks close together and turned forward. Color varíes from white to pink with faint mottling. Six specimens. LUCINIDAE Genus Lucina Bruguiere 1797 Lucina pensylvanica Linnaeus. Plate 8, Fig. 6A, 6B. 18 to 37 mm. Color: glossy white. Thin, straw-colored periostracum. Shell relatively thick, ovate, well inflated. Fresh specimens show numerous fine, concentric ridges. Strong posterior groove from beaks to ventral margin. Five specimens. Genus Codakia Scopoli 1777 Codakia cf. orbiculata Montagu. Plate 9, Fig. lA, lB, 3A, 3B. 8 to 11 mm. White. Obliquely rounded in outline. Large, elongate lunule. Numerous radial ribs extend to beaks; crossed by fine, concentric threads and coarser growth lines. Ten specimens. Codakia orbicularis Linnaeus. Plate 6, Fig. 2A, 2B. 25 to 75 mm. Orbicular in outline. Mature specimens modérately thick, heavy. Coarse, divaricate ribs are crossed by fine, concentric threads giving dbs beaded appearance. Beaks smooth, except for microscopic radial lines, yellowish. Lunule small, heart-shaped, nearly all in right valve. Exterior white, interior white to pale yellow; rose tinted interior margins on sorne specimens. Fifteen specimens. Genus Divaricella von Martens 1880 Divaricella quadrisulcata Orbigny. Plate 8, Fig. 3A, 3B. Slightly less than 25 mm. Orbic­ular, well inflated. Cream colored, glossy. Sculpture of fine, criss-cross grooves. One specimen. Divaricella dentata Wood. Plate 8, Fig. lA, lB. 25 to 37 mm. Orbicular, inflated. Color: cream. Sculpture of fine, criss-cross threads which extend beyond margins to form serrated edge; serration prominent on dorsal margin. 4 to 6 deeply impressed, con­centric growth lines. Six specimens. CHAMIDAE Genus Chama Linnaeus 1758 Chama macerophylla Gmelin. Plate 6, Fig. 5A, 5B. 31 to 69 mm in height. Heavy, roughly oval in outline. Concentric sculpture of irregular, fimbriated or foliated lamel­lae. lnner valve margins crenulated. Colors: yellow, pale pink, lavender. Eight speci­mens. CARDIIDAE Genus Trachycardium Morch 1853 Trachycardium isocardia Linnaeus. 53 mm in height, 44 mm wide. One beach specimen, dull white with flecks of pal e yellow. 32 rounded, radial ribs. Genus Trigoniocardia Dall 1900 Trigoniocardia media Linnaeus. Plate 8, Fig. lOA, lOB. One specimen 31 mm high. Shell thick, inflated. Posterior slope descends sharply. 34 strong, radial ribs, bearing chevron-shaped scales. Margins serrated. Escutcheon and lunule not defined. White splotched with light purple. Genus Laevicardium Swainson 1840 Laevicardium laevigatum Linnaeus. Plate 6, Fig. lA, lB. 31 to 40 mm in height, notas wide. Shell thin, well inflated, slightly oblique. Surface smooth except for micro­scopic sculpture. Glossy white with pink tinge near ligament; interior of sorne speci­mens flushed with pale yellow. lnner margins finely serrated. Six specimens. VENERIDAE Genus Antigona Schumacher 1817 Antigona listeri Gray. Plate 7, Fig. 6A, 6B. Slightly more than 75 mm. Thick, heavy, oblong-oval. Sculpture of numerous, low, radial riblets crossed by blade-like, serrated, concentric ridges. Gray-white with light brown splotches. Interior white, stainf"d purplish-black on posterior third. Two specimens. Antigona rigida Dillwyn. Plate 6, Fig. 3A, B. 62 mm, sub-circular in outline, inflated. White with long, chevon-shaped streaks of purplish brown. Sculpture of prominent, sharp, lamellate, concentric ridges; 1 to 4 concentric threads between ridges on upper half of valves. One specimen. Genus Chwne Mühlfeld 1811 Chione cancellata Linnaeus. Plate 8, Fig. 4. 25 mm in width, three-fourths as high. Low radial riblets crossed by sharp, blade-like, concentric ridges. Long, smooth escutcheon. Lunule heart-shaped with fine, vertical lines. Color: flat white, few irregular markings of dark brown and pink. Umbones pink. One specimen. PETRICOLIDAE Genus Petricola Lamarck 1801 Petricola lapicida Gmelin. Plate 9, Fig. 5A, 5B. 15 mm in height. Ovate, well inflated, grayish-white. Sculpture of minute, criss-cross threads. 5 to 7 irregular, wavy ribs on posterior end. Interior glossy white with pale green tinge. Three specimens. TELLINIDAE Genus Tellina Linnaeus 1758 Tellina interrupta Wood. Plate 7, Fig. lA, lB. 56 to 100 mm. Elongate, flattened, un­polished. Posterior end twisted. Sculpture of numerous, rough, evenly spaced, con­centric threads. Color: white with zigzag markings of light brown. Five specimens. Tellina radiata Linnaeus. Plate 7, Fig. 2A, 2B. 68 to 93 mm. Elongate. Porcelaneous. Shell creamy-white with broad rays of pinks and/or lavender. Interior all white or flushed with yellow. Beaks bright red. Three specimens. Tellina candeana Orbigny'. Plate 9, Fig. 4A, 4B. 12 to 15 mm. Moderately elongate, thin, fragile, translucent white. Sculpture of growth lines and numerous wavy, concentric threads which cross the shell at oblique angle. Twelve specimens. Genus Arcopagia Brown 1827 Arcopagia fausta Pultney. Plate 7, Fig. 5A, 5B. 68 to 88 mm. Oval in outline, relatively heavy. Smooth, except for lines of growth. Color: white with faint sheen. Interior glazed, flushed with pale yellow. Two specimens. Genus Strigilla Turton 1822 Strigilla mirabilis Philippi. Plate 9, Fig. 2A, 2B. 10 to 15 mm. Oval, moderately in­flated, translucent white. Sculpture of fine, impressed, criss-crossed lines. Pallial line does not reach anterior muscle scar. Inner margins smooth. Six specimens. Genus Apolymetis Salisbury 1929 Apolymetis intastriata Say. Plate 7, Fig. 3A, 3B. 63 mm. Oblong in outline. Dull white. Thin but strong. Posterior end twisted to the right. Strong radial ridge at posterior end of right valve, corresponding groove on left valve. Large pallial sinus. One speci­men. Mollusks of Alacran Reef, Campeche Bank, Mexico SCAPHOPODA S1PHONODENTALIIDAE Genus Cadulus Philippi 1844 Cadulus sp. Plate 3, Fig. 25. 19 mm, smooth. Apex with 4 well-defined notches. One specimen. DENTALIIDAE Genus Dentalium Linnaeus 1758 Dentalium sp. Plate 3, Fig. 2B. 23 mm, apex missing. White with apaque dots. Sculpture of numerous, low, llat ribs of varing widths. One specimen. AMPHINEURA IscHNOCHITONIDAE Genus lschrwchiton Gray 1847 lschnochiton sp. Plate 9, Fig. 12A, B. Slightly less than 25 mm, elongate, narrow. Color: grayish-green, speckled with dark green and black. Girdle covered with minute scales. Lateral areas raised, with wavy, beaded, longtitudinal riblets. Central areas similarly sculptured. End val ves concentrically beaded. Four specimens. Acknow ledgments Dr. Guillermo P. Salas, Director of the lnstitute de Geologia, Mexico, was most help· ful in making arrangements and, with Dr. F. Bonet and Amada Yánez, participated in many phases of the work. Thomas Wright assisted in curating specimens. Collecting the reef fauna was undertaken by many individuals including Mr. Charles M. Hoskin, Mr. J. Dan Powell, Mr. Henry Compton, Dr. Henry Hildebrand, and Dr. Donald W. Boyd. Officials and citizens of Mexico who assisted the work are C. Lic. Joaquin R. De LaGala, C. Administrador de la Aduana in Progresso; Sr. Candido Sanchez Cabanas, lighthouse keeper, Isla Perez; Lieutenant Gorge E. Roff, radio operator, Isla Perez; and Sr. F. Javier Campos, Jr. and Sr. F. Campos, Sr., Colon Travel Agency, Merida, Yucatan. We wish to express our sincere thanks to Dr. T. E. Pulley who helped identify many of the specimens reported here. Plates were photographed by G. Robert Adlington of the American Museum of Natural History. Literature Cited Abbott, Tucker R. 1955. American Seashells. D. Van Nostrand Company, Inc., New York. 541 p. Agassiz, Alexander. 1878-1879. Letter No. 'l to C P. Patterson, Superintendent Coast Guard Survey, Washington, D. C. Harv. Mus. Comp. Zoo!. 5(6): 1-19. ----. I8'88. Three Cruises of the United States Coast and Geodetic 'Steamer "Blake." Harv. Mus. Comp. Zool.1(1): 70--73. Kornicker, Louis S., F. Bonet, Ross Cann, and Charles M. Hoskin. '1959. Alacran Reef, Campeche Bank, Mexico. Pub!. Inst. Mar. Sci. Univ. Tex. 6: 1-22. Moore, Donald R. 1958. Notes on Blanquilla Reef. Pub!. Inst. 'Mar. Sci. Univ. Tex. 5: 1'51-1'55. Rehder, H. A., and R. T. Abbott. '1951 Sorne new and interesting mollusks from the deeper waters of the Gulf of Mexico. Rev. Soc. Malac. "Carlos de la Torre" 8(2): 53-66. Springer, Stewart, and 'Harvey R. Bullís, Jr. 1996. Collections by the Oregon in the Gulf of Mexico. Special scientific report: Fisheries No. 196, United States Department of the Interior, Fish and Wildlife Service. 134 p. Mollusks of Alacran Reef, Campeche Bank, Mexico PLATE 1 ALACRAN REEF GASTROPODS 2 to 3 times life size Text reference lA,B. Diodora listeri Orbigny ____ _ --·--·-··-·---·-·--·---------------··-----------····---········-·····-········-·············· 367 2A,B. Lucapina philippiana Finlay --·····-·-·-··-······-······ --·······----------·:______ _ __________________________367 3A,B. Diodora minute Lamarck ____ _ --·····-·-·--··-··-···-··-·-·-·-··-----····-·---··---·····----···-······ 367 4A,B. Lucapina suffusa Reeve ------------------------·-·-··--····--······--······-·-----------------·····--·-······-······· 367 5A,B. Acmaea pustulata pulcherrima Guilding --------·-----·····-··--············· --··--······--····-···-··-···-···-·--··-···-·--· ·367 6A,B. Acrnaea jamaicensis Gmelin ______ -------·--····-·-··------·····--·----·········-··-·---·········--····-················ 367 7A,B. Hemitoma emarginata de Blainville _------·-----·-·-···----···----···-···-------···------·-··-----··---···----······----······-· 367 8A,B. Cheilea equestris Linnaeus ------------------·------··--···-·---···----·-·-------·----···· ----···-------·-----····----···· 372 9A,B. Hipponix antiquatus Linnaeus _______ -------·····---·····----··-·· -----·----····-·--····----···-----·-···--·············· 372 Mollusks of Alacran Reef, Campeche Bank, Mexico PLATE 2 ALACRAN REEF GASTROPODS life size Text reference l. Cymatium gemmatum Reeve ....... ................ . ................................... 371 2. Cerithium literatum Born -········-·---···· . ................................ 371 3. Conus mus Hwass ... ·········-··--··-··········-.. ··--············-··--···-·-·--·---·· ............................... .... 377 4. Prunum labiatum Valenciennes -·--·-.................................. . .................................................. 377 5. Cyphoma gibbosum Linnaeus, two views, A, B .................. ····-······---·····-·-.... .... ......................... 373 6. C~lliostoma jujubinum Gmelin ...... ···········-··-·····---·-···-····--·---·-···--··-·--········-·-·· ............................. 368 ·7. Calliostoma zonamestum A. Adam~·, ............... -··-···-·-··-··-············--·--········ .. ····-··········-···---·---········ 367 '8. Nerita peloronta Linnaeus ········-·---····-····--........................................................... 369 9. Nerita tessellata Gmelin .'............................ -·-······-·-····-······ ........................................................... 369 10. Nerita versicolor Gmelin ................. ··········--··--............................................................................ 369 l~ 12. Turbo cailletii Fischer and Bernard ................................. .. ····-···-··············-·······--····-··-·-·----··-···· 368 13. Thais deltoidea Lamarck . ........................... ·-····················--······ ······-············-······ ·-·-···----·---··--· 375 14. Astraea americana Gmelin .............................. ························--·· ............................................... 369 15. Cymatium caribbaeum Clench and Turner ............................. ··--·---·-····--··-·--·---: ....... 374 16, 17. Vermicularia knorri Deshayes ....................... ................................................................... ............. 370 18. Petaloconchus cf. nigricans Dall, (x 2) ....................................................... ·----------------------------.. 370 Mollusks of Alacran Reef, Campeche Bank, Mexico PLATE 3 AL.A:CRAN REEF GASTROPODS AND SCAPHOPODS Text reference l. Prunum guttatum Dillwyn (x 2) -------------·--·----··-·-···········-·····-··---------------·········---------------------·--·-······ 377 2. Bulla sp. (x 2) -·····----·-·······-·····-·················· ····-··--···-···--····----------·-··------·········-------·················-··--······----378 3. Atys caribaea Orbigny (x 2) --------·---·----·····--'······--·-·······-···--------··--·--·------·-·····----------------: _________________ 378 4. Nodilittorina tuberculata Menke (x 2) -----······---------·-··------------------------·····-··········--·-·--·---··-·---·-·····--· 370 ,5. Drupa nodulosa C. B. Adams (x 2) ··-----------·-··----------··---········---------------------·····------·--··--·-·--·----······--·--374 6, and 8. Littorina ziczac Gmelin (x 2) ---·----------------------------------------·---------·--------------·---------·--·-·--·--········ 369 7. N eritina virgínea Linnaeus (x 5) ----·····----------------------······-------------·-···-·----------····--------···--·---------·'·-------369 9. Batillaria minima Gmelin (x 5) ----·-----·-······-------------------····---------······---------------------·--·------··········--······· 371 10. Cerithium algicola C. B. Adams (x 2) ··--·------···-··-------··--·---·---····--------·-··----------------·---·-·-·------------·--·-· 371 11. Alaba sp. (;,e 5) --------········-------····----------------·--------··----------··-----···--···-----------·-·· ·····---------------------------·------371 12. Seila adamsi H. C. Lea (x 5) ---------------------------------------------------··-------······----·-····----------------------·--···--···· 371 13. Rissoina cancellata Philippi (x 5) ····-------------------------------·----------·-------------·····-------·--------·-······-······----370 14. Rissoina multicostata C. B. Adams (x 5) ----------------------------------------------------·---------------------:.__ ________ 370 15. Pusia gemmata Sowerby (x 5) --·-··--------------------------------------------------··-··········--------------------------·--·--------377 16. Rissoina chesneli Michaud (x 10) ------·-·---·······························-·········------·-···········-·------------·----------------370 17. Balcis sp. (x 10) ····--------········------......... -'····--··--·-·······------------·-···········--·--·-·-······-··------------·------··-··-······ 372 18. Odostomia sp. (x 10) -···················-············-·········-------····-······-·----·········--·-·--·······--·----····--··--··---------······ 378 19. Tricolia cf. thalassicola Robertson (x 5) ---·-----------------·-···--·------------····-----·-·······--------·-·····--·-·---------··· 369 20. Sinum perspectivum Say (x 2) ······-······--······----------------------------------------·----------·-------------···----------------· 373 21. Cyclostrema cancellatum Marryat (x 10) ----------·-·······-···············--·------···-------···------------------·-----------· 368 22. Caecum cooperi S. Smith (x 10) ---------·····--··----·------------------------------------·---····-----------------------··----------· 370 23. Caecum floridanum Stimpson (x 10) ···--······--------·---------------·······--·-··------·---------·-·--·-··········· ·············-370 24. Caecum nebulosum Rehder (x 10) -----------···------------------------------·-··------------------------------------------·········-371 25. Cadulus sp. (x 10) ------------·---·-----------------------·-----------·-------··----------·------··········--···--------······--·······-----········ 384 26. Dentalium sp. (x 10) -·········---------------------------------------------------··-----·------------------------'---------····:·----·-··-:--.. 384 Mollusks. o/ Alacran Reef, Campeche Bank, Mexico . PLATE 4 ALA'CRAN REEF GASTROPODS 3 times !ife size Text reference l. Bailya intricata Dall .............................................................. ................... . ................. 375 2. Nassarius ambig~'fS Pulteney :················ ........................................................................................... 376 3. Cerithium variabile C. B. Adams ........... . .............. , .................................................................. 371 4. Triphora decorata C. B. Adams-............................................................................................ . 372 5. Columbella mercatoria Linnaeus 375 6. Anachis pulchella Sowerby .......................................................................................................... 375 7. NitideUa nitidula Sowerby .... ········ii<·'········· .......................••......................................................... 375 8. Hyalina avena Valenciennes ................ .. ............... . ................................ 375 9. Olivella nivea Gmelin .......... ..................................................... . ................................ 376 ,:¡... 10. Atys sande.rsoni Dall ...............................................................!>',ro························································· 378 11. P;;sicula sp . ................................ ...:~;,....... . .....................~,·-······················ ·········· 377 12.· Haminoea succinea Conrad .. ·-··--············ ··················-----~---·---···---·--·--······ 378 13. Smaragdia viridis Linnaeus .. . .................................................................................... · 369 14. Batillaria minima Gmelin .................... ···········································---···-··--·--·-·----··-----·---···-······· 371 15. Arene cf. cruentata Muhlfeld 368 16. Modul1JS ' modulus Linnaeus . ··················· ················································· ...................... 371 17. Trivio sufjusa Gray ......................... ········································--·-·-----····-··--·······---··-·--··-····-··-...... 373 18. Calliostoma sp . ....................... -····························---·-····-·-................ -···--·-·--··-·--------·--···--·-·-----·············· 368 19. Epitonium sp . ..................... . ··························•··········································-·---·-···--··--·------·-·-----·--· 372 20. Cerithium ebumeum Bruguiere ······----··-·--····-··········-············································ 371 Mollusks o/ Alacran Reef, Campeche Bank, Mexico PLATE 5 ALACRAN REEF GASTROPODS 1h to % life size , Text reference 1, 2. Strombus gigas Linne (x %) .............................................. ......................................................... 372 3. Xancus angulatus Solander (x 'f2) ....................................~......................................................... 376 4, 8. F ascwlaria tulipa Linnaeus (X 1h) ................................................................................................ 376 5, 10. Strombus raninas Gmelin (x %) ................................................................................................ 373 6, 9. Strombus costatus Gmelin (x 1h) ................ .........................................:'·............:................:..~~-· . 372 7. Busycon spiratum Lamarck (x 'f2) ..............................................................................................;;;;376 ll, 16, Tonna galea Linnaeus (x %) ................................................~.................................................,,...'.t:374 ~:: ~::n~:::u~1::a~x(~~~..::::::::::::: :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::··:::·~~: 14. Leucozonia nassa Gmelin (x %) ..........................................................:..,..... -...................... _ .......: 3°76 15. Natica can~ena Linnaeus (x % ) ..................~.................:... : ..............................:..............;,:'...~....:.... ;á73 ~' . . 17. Astraea caelata Gmelin (x %) ................................................................. : ................... : ................·ª69 18. Astraea longispina Lamarck (x %) .:-...........................................................:................................ 3~ 19.' Cymatium pileare Linnaeus (x % ) ................._.........................,........:....:....,...............................:-. '.374 Mollusks of Alacran Reef, Campeche Bank, Mexico PLATE 6 ALACRAN REEF PELECYPODS 1h to % life size Text refere nce lA,B. 2A,B. 3A,B. Laevicardium laevigatum Linnaeus (x %) ................... . ·············· ·· ···•··• ························ Codakia orbicularis Linnaeus (x %) ..................................................................................... Antigona rigida Dillwyn (x 1/z) ...... . ............................................................. ....................... 382 381 382 4A,B,C. Ostrea frons Linnaeus (x % ) ........ ...................................................................................... 381 SA,B. Chama macerophylla Gmelin (x %) ............................................................... ........................ 382 6A,B. Pinctada radiata Leach (x %) ........................................... ...................................................... 380 7A,B. Arca umbonata Lamarck (x %) .... ......................................................................................... 378 8A,B. Arca zebra Swainson (x % ) ................................................................................................... 378 9. Pinctada radiata Leach ( x % ) ................................................................................................. 380 Mollusks of Alacran Reef, Campeche Bank, Mexico PLATE 7 ALACRAN REEF PELECYPODS 1h to % life size Text reference lA,B. Tellina interrupta Wo